diff --git a/.eslintrc.yml b/.eslintrc.yml
index bed57fbc..65f1dce6 100644
--- a/.eslintrc.yml
+++ b/.eslintrc.yml
@@ -11,3 +11,4 @@ rules:
   block-scoped-var: error
   eqeqeq: error
   no-warning-comments: warn
+  no-var: error
diff --git a/samples/mailjet.js b/samples/mailjet.js
index ab368694..ece5d102 100644
--- a/samples/mailjet.js
+++ b/samples/mailjet.js
@@ -16,10 +16,10 @@
 'use strict';
 
 // [START send]
-var mailer = require('nodemailer');
-var smtp = require('nodemailer-smtp-transport');
+let mailer = require('nodemailer');
+let smtp = require('nodemailer-smtp-transport');
 
-var transport = mailer.createTransport(
+let transport = mailer.createTransport(
   smtp({
     host: 'in.mailjet.com',
     port: 2525,
diff --git a/samples/sendgrid.js b/samples/sendgrid.js
index 95f87370..79ad26e7 100644
--- a/samples/sendgrid.js
+++ b/samples/sendgrid.js
@@ -15,11 +15,11 @@
 
 // [START send]
 // This sample is based off of https://www.npmjs.com/package/sendgrid#without-mail-helper-class
-var Sendgrid = require('sendgrid')(
+let Sendgrid = require('sendgrid')(
   process.env.SENDGRID_API_KEY || '<your-sendgrid-api-key>'
 );
 
-var request = Sendgrid.emptyRequest({
+let request = Sendgrid.emptyRequest({
   method: 'POST',
   path: '/v3/mail/send',
   body: {
diff --git a/samples/startup-script/system-test/index.test.js b/samples/startup-script/system-test/index.test.js
index 719b4718..55f1c654 100644
--- a/samples/startup-script/system-test/index.test.js
+++ b/samples/startup-script/system-test/index.test.js
@@ -35,7 +35,7 @@ test.cb(`should list vms`, t => {
 });
 
 test.cb(`should create vm`, t => {
-  var TESTS_PREFIX = 'gcloud-tests-';
+  let TESTS_PREFIX = 'gcloud-tests-';
   const name = generateName('vm-with-apache');
 
   function generateName(customPrefix) {
diff --git a/src/address.js b/src/address.js
index 74c756af..8c0a6205 100644
--- a/src/address.js
+++ b/src/address.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /**
  * An Address object allows you to interact with a Google Compute Engine
@@ -37,7 +37,7 @@ var util = require('util');
  * const address = region.address('address1');
  */
 function Address(region, name) {
-  var methods = {
+  let methods = {
     /**
      * Create an address.
      *
@@ -216,7 +216,7 @@ util.inherits(Address, common.ServiceObject);
 Address.prototype.delete = function(callback) {
   callback = callback || common.util.noop;
 
-  var region = this.region;
+  let region = this.region;
 
   this.request(
     {
@@ -229,7 +229,7 @@ Address.prototype.delete = function(callback) {
         return;
       }
 
-      var operation = region.operation(resp.name);
+      let operation = region.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, operation, resp);
diff --git a/src/autoscaler.js b/src/autoscaler.js
index 1c29d3b1..9a27e25e 100644
--- a/src/autoscaler.js
+++ b/src/autoscaler.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /*! Developer Documentation
  *
@@ -41,7 +41,7 @@ var util = require('util');
  * const autoscaler = zone.autoscaler('autoscaler-name');
  */
 function Autoscaler(zone, name) {
-  var methods = {
+  let methods = {
     /**
      * Create an autoscaler.
      *
@@ -231,7 +231,7 @@ util.inherits(Autoscaler, common.ServiceObject);
 Autoscaler.prototype.delete = function(callback) {
   callback = callback || common.util.noop;
 
-  var zone = this.zone;
+  let zone = this.zone;
 
   common.ServiceObject.prototype.delete.call(this, function(err, resp) {
     if (err) {
@@ -239,7 +239,7 @@ Autoscaler.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = zone.operation(resp.name);
+    let operation = zone.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
@@ -283,7 +283,7 @@ Autoscaler.prototype.delete = function(callback) {
  * });
  */
 Autoscaler.prototype.setMetadata = function(metadata, callback) {
-  var zone = this.zone;
+  let zone = this.zone;
 
   callback = callback || common.util.noop;
 
@@ -306,7 +306,7 @@ Autoscaler.prototype.setMetadata = function(metadata, callback) {
         return;
       }
 
-      var operation = zone.operation(resp.name);
+      let operation = zone.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, operation, resp);
diff --git a/src/disk.js b/src/disk.js
index 9cce1409..75f6c799 100644
--- a/src/disk.js
+++ b/src/disk.js
@@ -16,13 +16,13 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var format = require('string-format-obj');
-var is = require('is');
-var util = require('util');
+let common = require('@google-cloud/common');
+let extend = require('extend');
+let format = require('string-format-obj');
+let is = require('is');
+let util = require('util');
 
-var Snapshot = require('./snapshot.js');
+let Snapshot = require('./snapshot.js');
 
 /**
  * A Disk object allows you to interact with a Google Compute Engine disk.
@@ -41,7 +41,7 @@ var Snapshot = require('./snapshot.js');
  * const disk = zone.disk('disk1');
  */
 function Disk(zone, name) {
-  var methods = {
+  let methods = {
     /**
      * Create a persistent disk.
      *
@@ -261,8 +261,8 @@ Disk.formatName_ = function(zone, name) {
  * });
  */
 Disk.prototype.createSnapshot = function(name, options, callback) {
-  var self = this;
-  var zone = this.zone;
+  let self = this;
+  let zone = this.zone;
 
   if (is.fn(options)) {
     callback = options;
@@ -283,9 +283,9 @@ Disk.prototype.createSnapshot = function(name, options, callback) {
         return;
       }
 
-      var snapshot = self.snapshot(name);
+      let snapshot = self.snapshot(name);
 
-      var operation = zone.operation(resp.name);
+      let operation = zone.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, snapshot, operation, resp);
@@ -324,7 +324,7 @@ Disk.prototype.createSnapshot = function(name, options, callback) {
  * });
  */
 Disk.prototype.delete = function(callback) {
-  var zone = this.zone;
+  let zone = this.zone;
 
   callback = callback || common.util.noop;
 
@@ -334,7 +334,7 @@ Disk.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = zone.operation(resp.name);
+    let operation = zone.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
diff --git a/src/firewall.js b/src/firewall.js
index dacf7f29..c1cf60be 100644
--- a/src/firewall.js
+++ b/src/firewall.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /**
  * A Firewall object allows you to interact with a Google Compute Engine
@@ -36,7 +36,7 @@ var util = require('util');
  * const firewall = compute.firewall('tcp-3000');
  */
 function Firewall(compute, name) {
-  var methods = {
+  let methods = {
     /**
      * Create a firewall.
      *
@@ -222,7 +222,7 @@ util.inherits(Firewall, common.ServiceObject);
  * });
  */
 Firewall.prototype.delete = function(callback) {
-  var compute = this.compute;
+  let compute = this.compute;
 
   callback = callback || common.util.noop;
 
@@ -232,7 +232,7 @@ Firewall.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = compute.operation(resp.name);
+    let operation = compute.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
@@ -275,7 +275,7 @@ Firewall.prototype.delete = function(callback) {
  * });
  */
 Firewall.prototype.setMetadata = function(metadata, callback) {
-  var compute = this.compute;
+  let compute = this.compute;
 
   callback = callback || common.util.noop;
 
@@ -295,7 +295,7 @@ Firewall.prototype.setMetadata = function(metadata, callback) {
         return;
       }
 
-      var operation = compute.operation(resp.name);
+      let operation = compute.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, operation, resp);
diff --git a/src/health-check.js b/src/health-check.js
index 4dc46203..3c89d125 100644
--- a/src/health-check.js
+++ b/src/health-check.js
@@ -16,10 +16,10 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var is = require('is');
-var util = require('util');
+let common = require('@google-cloud/common');
+let extend = require('extend');
+let is = require('is');
+let util = require('util');
 
 /**
  * Health checks ensure that Compute Engine forwards new connections only to
@@ -44,7 +44,7 @@ var util = require('util');
  * const healthCheck = gce.healthCheck('health-check-name');
  */
 function HealthCheck(compute, name, options) {
-  var methods = {
+  let methods = {
     /**
      * Create an HTTP or HTTPS health check.
      *
@@ -167,7 +167,7 @@ function HealthCheck(compute, name, options) {
 
   options = options || {};
 
-  var https = options.https;
+  let https = options.https;
 
   /**
    * The parent {@link Compute} instance of this {@link HealthCheck} instance.
@@ -231,7 +231,7 @@ util.inherits(HealthCheck, common.ServiceObject);
  * });
  */
 HealthCheck.prototype.delete = function(callback) {
-  var compute = this.compute;
+  let compute = this.compute;
 
   callback = callback || common.util.noop;
 
@@ -241,7 +241,7 @@ HealthCheck.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = compute.operation(resp.name);
+    let operation = compute.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
@@ -286,11 +286,11 @@ HealthCheck.prototype.delete = function(callback) {
  * });
  */
 HealthCheck.prototype.setMetadata = function(metadata, callback) {
-  var compute = this.compute;
+  let compute = this.compute;
 
   callback = callback || common.util.noop;
 
-  var setMetadata = common.ServiceObject.prototype.setMetadata;
+  let setMetadata = common.ServiceObject.prototype.setMetadata;
 
   setMetadata.call(this, metadata, function(err, resp) {
     if (err) {
@@ -298,7 +298,7 @@ HealthCheck.prototype.setMetadata = function(metadata, callback) {
       return;
     }
 
-    var operation = compute.operation(resp.name);
+    let operation = compute.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
diff --git a/src/image.js b/src/image.js
index 28896904..f18b670b 100644
--- a/src/image.js
+++ b/src/image.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /**
  * An Image object allows you to interact with a Google Compute Engine image.
@@ -35,7 +35,7 @@ var util = require('util');
  * const image = compute.image('image-name');
  */
 function Image(compute, name) {
-  var methods = {
+  let methods = {
     /**
      * Create an image.
      *
@@ -194,7 +194,7 @@ util.inherits(Image, common.ServiceObject);
  * });
  */
 Image.prototype.delete = function(callback) {
-  var compute = this.parent;
+  let compute = this.parent;
 
   callback = callback || common.util.noop;
 
@@ -204,7 +204,7 @@ Image.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = compute.operation(resp.name);
+    let operation = compute.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
diff --git a/src/index.js b/src/index.js
index 4784970e..21858a10 100644
--- a/src/index.js
+++ b/src/index.js
@@ -16,24 +16,24 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var format = require('string-format-obj');
-var is = require('is');
-var util = require('util');
-
-var Firewall = require('./firewall.js');
-var HealthCheck = require('./health-check.js');
-var Network = require('./network.js');
-var Operation = require('./operation.js');
-var Project = require('./project.js');
-var Region = require('./region.js');
-var Rule = require('./rule.js');
-var Service = require('./service.js');
-var Snapshot = require('./snapshot.js');
-var Zone = require('./zone.js');
-var Image = require('./image.js');
+let arrify = require('arrify');
+let common = require('@google-cloud/common');
+let extend = require('extend');
+let format = require('string-format-obj');
+let is = require('is');
+let util = require('util');
+
+let Firewall = require('./firewall.js');
+let HealthCheck = require('./health-check.js');
+let Network = require('./network.js');
+let Operation = require('./operation.js');
+let Project = require('./project.js');
+let Region = require('./region.js');
+let Rule = require('./rule.js');
+let Service = require('./service.js');
+let Snapshot = require('./snapshot.js');
+let Zone = require('./zone.js');
+let Image = require('./image.js');
 
 /**
  * @typedef {object} ClientConfig
@@ -81,7 +81,7 @@ var Image = require('./image.js');
 function Compute(options) {
   options = common.util.normalizeArguments(this, options);
 
-  var config = {
+  let config = {
     baseUrl: 'https://www.googleapis.com/compute/v1',
     scopes: ['https://www.googleapis.com/auth/compute'],
     packageJson: require('../package.json'),
@@ -151,7 +151,7 @@ util.inherits(Compute, common.Service);
  * });
  */
 Compute.prototype.createFirewall = function(name, config, callback) {
-  var self = this;
+  let self = this;
 
   if (!is.string(name)) {
     throw new Error('A firewall name must be provided.');
@@ -161,19 +161,19 @@ Compute.prototype.createFirewall = function(name, config, callback) {
     throw new Error('A firewall configuration object must be provided.');
   }
 
-  var body = extend({}, config, {
+  let body = extend({}, config, {
     name: name,
   });
 
   if (body.protocols) {
     body.allowed = arrify(body.allowed);
 
-    for (var protocol in body.protocols) {
-      var allowedConfig = {
+    for (let protocol in body.protocols) {
+      let allowedConfig = {
         IPProtocol: protocol,
       };
 
-      var ports = body.protocols[protocol];
+      let ports = body.protocols[protocol];
 
       if (ports === false || ports.length === 0) {
         continue;
@@ -210,9 +210,9 @@ Compute.prototype.createFirewall = function(name, config, callback) {
         return;
       }
 
-      var firewall = self.firewall(name);
+      let firewall = self.firewall(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, firewall, operation, resp);
@@ -268,7 +268,7 @@ Compute.prototype.createFirewall = function(name, config, callback) {
  * });
  */
 Compute.prototype.createHealthCheck = function(name, options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -279,11 +279,11 @@ Compute.prototype.createHealthCheck = function(name, options, callback) {
     throw new Error('A health check name must be provided.');
   }
 
-  var body = extend({}, options, {
+  let body = extend({}, options, {
     name: name,
   });
 
-  var https = options.https;
+  let https = options.https;
   delete body.https;
 
   if (body.interval) {
@@ -308,11 +308,11 @@ Compute.prototype.createHealthCheck = function(name, options, callback) {
         return;
       }
 
-      var healthCheck = self.healthCheck(name, {
+      let healthCheck = self.healthCheck(name, {
         https: https,
       });
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, healthCheck, operation, resp);
@@ -355,7 +355,7 @@ Compute.prototype.createHealthCheck = function(name, options, callback) {
  * });
  */
 Compute.prototype.createImage = function(name, disk, options, callback) {
-  var self = this;
+  let self = this;
 
   if (!common.util.isCustomType(disk, 'Disk')) {
     throw new Error('A Disk object is required.');
@@ -366,7 +366,7 @@ Compute.prototype.createImage = function(name, disk, options, callback) {
     options = {};
   }
 
-  var body = extend(
+  let body = extend(
     {
       name: name,
       sourceDisk: format('zones/{zoneName}/disks/{diskName}', {
@@ -388,9 +388,9 @@ Compute.prototype.createImage = function(name, disk, options, callback) {
         callback(err, null, resp);
         return;
       }
-      var image = self.image(name);
+      let image = self.image(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, image, operation, resp);
@@ -445,9 +445,9 @@ Compute.prototype.createImage = function(name, disk, options, callback) {
  * });
  */
 Compute.prototype.createNetwork = function(name, config, callback) {
-  var self = this;
+  let self = this;
 
-  var body = extend({}, config, {
+  let body = extend({}, config, {
     name: name,
   });
 
@@ -473,9 +473,9 @@ Compute.prototype.createNetwork = function(name, config, callback) {
         return;
       }
 
-      var network = self.network(name);
+      let network = self.network(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, network, operation, resp);
@@ -542,9 +542,9 @@ Compute.prototype.createNetwork = function(name, config, callback) {
  * });
  */
 Compute.prototype.createRule = function(name, config, callback) {
-  var self = this;
+  let self = this;
 
-  var body = extend({}, config, {
+  let body = extend({}, config, {
     name: name,
   });
 
@@ -575,9 +575,9 @@ Compute.prototype.createRule = function(name, config, callback) {
         return;
       }
 
-      var rule = self.rule(name);
+      let rule = self.rule(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, rule, operation, resp);
@@ -633,9 +633,9 @@ Compute.prototype.createRule = function(name, config, callback) {
  * });
  */
 Compute.prototype.createService = function(name, config, callback) {
-  var self = this;
+  let self = this;
 
-  var body = extend({}, config, {
+  let body = extend({}, config, {
     name: name,
   });
 
@@ -651,9 +651,9 @@ Compute.prototype.createService = function(name, config, callback) {
         return;
       }
 
-      var service = self.service(name);
+      let service = self.service(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, service, operation, resp);
@@ -734,7 +734,7 @@ Compute.prototype.firewall = function(name) {
  * });
  */
 Compute.prototype.getAddresses = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -754,7 +754,7 @@ Compute.prototype.getAddresses = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -762,14 +762,14 @@ Compute.prototype.getAddresses = function(options, callback) {
         });
       }
 
-      var regions = resp.items || {};
+      let regions = resp.items || {};
 
-      var addresses = Object.keys(regions).reduce(function(acc, regionName) {
-        var region = self.region(regionName.replace('regions/', ''));
-        var regionAddresses = regions[regionName].addresses || [];
+      let addresses = Object.keys(regions).reduce(function(acc, regionName) {
+        let region = self.region(regionName.replace('regions/', ''));
+        let regionAddresses = regions[regionName].addresses || [];
 
         regionAddresses.forEach(function(address) {
-          var addressInstance = region.address(address.name);
+          let addressInstance = region.address(address.name);
           addressInstance.metadata = address;
           acc.push(addressInstance);
         });
@@ -868,7 +868,7 @@ Compute.prototype.getAddressesStream = common.paginator.streamify(
  * });
  */
 Compute.prototype.getAutoscalers = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -888,7 +888,7 @@ Compute.prototype.getAutoscalers = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -896,18 +896,18 @@ Compute.prototype.getAutoscalers = function(options, callback) {
         });
       }
 
-      var zones = resp.items || {};
+      let zones = resp.items || {};
 
-      var autoscalers = Object.keys(zones).reduce(function(acc, zoneName) {
+      let autoscalers = Object.keys(zones).reduce(function(acc, zoneName) {
         if (zoneName.indexOf('zones/') !== 0) {
           return acc;
         }
 
-        var zone = self.zone(zoneName.replace('zones/', ''));
-        var zoneAutoscalers = zones[zoneName].autoscalers || [];
+        let zone = self.zone(zoneName.replace('zones/', ''));
+        let zoneAutoscalers = zones[zoneName].autoscalers || [];
 
         zoneAutoscalers.forEach(function(autoscaler) {
-          var autoscalerInstance = zone.autoscaler(autoscaler.name);
+          let autoscalerInstance = zone.autoscaler(autoscaler.name);
           autoscalerInstance.metadata = autoscaler;
           acc.push(autoscalerInstance);
         });
@@ -1005,7 +1005,7 @@ Compute.prototype.getAutoscalersStream = common.paginator.streamify(
  * });
  */
 Compute.prototype.getDisks = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1025,7 +1025,7 @@ Compute.prototype.getDisks = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1033,14 +1033,14 @@ Compute.prototype.getDisks = function(options, callback) {
         });
       }
 
-      var zones = resp.items || {};
+      let zones = resp.items || {};
 
-      var disks = Object.keys(zones).reduce(function(acc, zoneName) {
-        var zone = self.zone(zoneName.replace('zones/', ''));
-        var disks = zones[zoneName].disks || [];
+      let disks = Object.keys(zones).reduce(function(acc, zoneName) {
+        let zone = self.zone(zoneName.replace('zones/', ''));
+        let disks = zones[zoneName].disks || [];
 
         disks.forEach(function(disk) {
-          var diskInstance = zone.disk(disk.name);
+          let diskInstance = zone.disk(disk.name);
           diskInstance.metadata = disk;
           acc.push(diskInstance);
         });
@@ -1138,7 +1138,7 @@ Compute.prototype.getDisksStream = common.paginator.streamify('getDisks');
  * });
  */
 Compute.prototype.getInstanceGroups = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1158,7 +1158,7 @@ Compute.prototype.getInstanceGroups = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1166,14 +1166,14 @@ Compute.prototype.getInstanceGroups = function(options, callback) {
         });
       }
 
-      var zones = resp.items || {};
+      let zones = resp.items || {};
 
-      var instanceGroups = Object.keys(zones).reduce(function(acc, zoneName) {
-        var zone = self.zone(zoneName.replace('zones/', ''));
-        var instanceGroups = zones[zoneName].instanceGroups || [];
+      let instanceGroups = Object.keys(zones).reduce(function(acc, zoneName) {
+        let zone = self.zone(zoneName.replace('zones/', ''));
+        let instanceGroups = zones[zoneName].instanceGroups || [];
 
         instanceGroups.forEach(function(group) {
-          var instanceGroupInstance = zone.instanceGroup(group.name);
+          let instanceGroupInstance = zone.instanceGroup(group.name);
           instanceGroupInstance.metadata = group;
           acc.push(instanceGroupInstance);
         });
@@ -1270,7 +1270,7 @@ Compute.prototype.getInstanceGroupsStream = common.paginator.streamify(
  * });
  */
 Compute.prototype.getFirewalls = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1290,7 +1290,7 @@ Compute.prototype.getFirewalls = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1298,8 +1298,8 @@ Compute.prototype.getFirewalls = function(options, callback) {
         });
       }
 
-      var firewalls = (resp.items || []).map(function(firewall) {
-        var firewallInstance = self.firewall(firewall.name);
+      let firewalls = (resp.items || []).map(function(firewall) {
+        let firewallInstance = self.firewall(firewall.name);
         firewallInstance.metadata = firewall;
         return firewallInstance;
       });
@@ -1394,7 +1394,7 @@ Compute.prototype.getFirewallsStream = common.paginator.streamify(
  * });
  */
 Compute.prototype.getHealthChecks = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1403,7 +1403,7 @@ Compute.prototype.getHealthChecks = function(options, callback) {
 
   options = extend({}, options);
 
-  var https = options.https;
+  let https = options.https;
   delete options.https;
 
   this.request(
@@ -1417,7 +1417,7 @@ Compute.prototype.getHealthChecks = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1425,8 +1425,8 @@ Compute.prototype.getHealthChecks = function(options, callback) {
         });
       }
 
-      var healthChecks = (resp.items || []).map(function(healthCheck) {
-        var healthCheckInstance = self.healthCheck(healthCheck.name, {
+      let healthChecks = (resp.items || []).map(function(healthCheck) {
+        let healthCheckInstance = self.healthCheck(healthCheck.name, {
           https: https,
         });
         healthCheckInstance.metadata = healthCheck;
@@ -1520,7 +1520,7 @@ Compute.prototype.getHealthChecksStream = common.paginator.streamify(
  * });
  */
 Compute.prototype.getImages = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1540,7 +1540,7 @@ Compute.prototype.getImages = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1548,8 +1548,8 @@ Compute.prototype.getImages = function(options, callback) {
         });
       }
 
-      var images = (resp.items || []).map(function(image) {
-        var imageInstance = self.image(image.name);
+      let images = (resp.items || []).map(function(image) {
+        let imageInstance = self.image(image.name);
         imageInstance.metadata = image;
         return imageInstance;
       });
@@ -1644,7 +1644,7 @@ Compute.prototype.getImagesStream = common.paginator.streamify('getImages');
  * });
  */
 Compute.prototype.getMachineTypes = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1664,7 +1664,7 @@ Compute.prototype.getMachineTypes = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1672,14 +1672,14 @@ Compute.prototype.getMachineTypes = function(options, callback) {
         });
       }
 
-      var zones = resp.items || {};
+      let zones = resp.items || {};
 
-      var machineTypes = Object.keys(zones).reduce(function(acc, zoneName) {
-        var zone = self.zone(zoneName.replace('zones/', ''));
-        var machineTypesByZone = zones[zoneName].machineTypes || [];
+      let machineTypes = Object.keys(zones).reduce(function(acc, zoneName) {
+        let zone = self.zone(zoneName.replace('zones/', ''));
+        let machineTypesByZone = zones[zoneName].machineTypes || [];
 
         machineTypesByZone.forEach(function(machineType) {
-          var machineTypeInstance = zone.machineType(machineType.name);
+          let machineTypeInstance = zone.machineType(machineType.name);
           machineTypeInstance.metadata = machineType;
           acc.push(machineTypeInstance);
         });
@@ -1778,7 +1778,7 @@ Compute.prototype.getMachineTypesStream = common.paginator.streamify(
  * });
  */
 Compute.prototype.getNetworks = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1798,7 +1798,7 @@ Compute.prototype.getNetworks = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1806,8 +1806,8 @@ Compute.prototype.getNetworks = function(options, callback) {
         });
       }
 
-      var networks = (resp.items || []).map(function(network) {
-        var networkInstance = self.network(network.name);
+      let networks = (resp.items || []).map(function(network) {
+        let networkInstance = self.network(network.name);
         networkInstance.metadata = network;
         return networkInstance;
       });
@@ -1900,7 +1900,7 @@ Compute.prototype.getNetworksStream = common.paginator.streamify('getNetworks');
  * });
  */
 Compute.prototype.getOperations = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1920,7 +1920,7 @@ Compute.prototype.getOperations = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1928,8 +1928,8 @@ Compute.prototype.getOperations = function(options, callback) {
         });
       }
 
-      var operations = (resp.items || []).map(function(operation) {
-        var operationInstance = self.operation(operation.name);
+      let operations = (resp.items || []).map(function(operation) {
+        let operationInstance = self.operation(operation.name);
         operationInstance.metadata = operation;
         return operationInstance;
       });
@@ -2025,7 +2025,7 @@ Compute.prototype.getOperationsStream = common.paginator.streamify(
  * });
  */
 Compute.prototype.getRegions = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -2043,7 +2043,7 @@ Compute.prototype.getRegions = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -2051,8 +2051,8 @@ Compute.prototype.getRegions = function(options, callback) {
         });
       }
 
-      var regions = resp.items.map(function(region) {
-        var regionInstance = self.region(region.name);
+      let regions = resp.items.map(function(region) {
+        let regionInstance = self.region(region.name);
         regionInstance.metadata = region;
         return regionInstance;
       });
@@ -2145,7 +2145,7 @@ Compute.prototype.getRegionsStream = common.paginator.streamify('getRegions');
  * });
  */
 Compute.prototype.getRules = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -2165,7 +2165,7 @@ Compute.prototype.getRules = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -2173,8 +2173,8 @@ Compute.prototype.getRules = function(options, callback) {
         });
       }
 
-      var rules = (resp.items || []).map(function(rule) {
-        var ruleInstance = self.rule(rule.name);
+      let rules = (resp.items || []).map(function(rule) {
+        let ruleInstance = self.rule(rule.name);
         ruleInstance.metadata = rule;
         return ruleInstance;
       });
@@ -2267,7 +2267,7 @@ Compute.prototype.getRulesStream = common.paginator.streamify('getRules');
  * });
  */
 Compute.prototype.getServices = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -2287,7 +2287,7 @@ Compute.prototype.getServices = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -2295,8 +2295,8 @@ Compute.prototype.getServices = function(options, callback) {
         });
       }
 
-      var services = (resp.items || []).map(function(service) {
-        var serviceInstance = self.service(service.name);
+      let services = (resp.items || []).map(function(service) {
+        let serviceInstance = self.service(service.name);
         serviceInstance.metadata = service;
         return serviceInstance;
       });
@@ -2389,7 +2389,7 @@ Compute.prototype.getServicesStream = common.paginator.streamify('getServices');
  * });
  */
 Compute.prototype.getSnapshots = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -2409,7 +2409,7 @@ Compute.prototype.getSnapshots = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -2417,8 +2417,8 @@ Compute.prototype.getSnapshots = function(options, callback) {
         });
       }
 
-      var snapshots = (resp.items || []).map(function(snapshot) {
-        var snapshotInstance = self.snapshot(snapshot.name);
+      let snapshots = (resp.items || []).map(function(snapshot) {
+        let snapshotInstance = self.snapshot(snapshot.name);
         snapshotInstance.metadata = snapshot;
         return snapshotInstance;
       });
@@ -2513,7 +2513,7 @@ Compute.prototype.getSnapshotsStream = common.paginator.streamify(
  * });
  */
 Compute.prototype.getSubnetworks = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -2533,7 +2533,7 @@ Compute.prototype.getSubnetworks = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -2541,14 +2541,14 @@ Compute.prototype.getSubnetworks = function(options, callback) {
         });
       }
 
-      var regions = resp.items || {};
+      let regions = resp.items || {};
 
-      var subnetworks = Object.keys(regions).reduce(function(acc, regionName) {
-        var region = self.region(regionName.replace('regions/', ''));
-        var subnetworks = regions[regionName].subnetworks || [];
+      let subnetworks = Object.keys(regions).reduce(function(acc, regionName) {
+        let region = self.region(regionName.replace('regions/', ''));
+        let subnetworks = regions[regionName].subnetworks || [];
 
         subnetworks.forEach(function(subnetwork) {
-          var subnetworkInstance = region.subnetwork(subnetwork.name);
+          let subnetworkInstance = region.subnetwork(subnetwork.name);
           subnetworkInstance.metadata = subnetwork;
           acc.push(subnetworkInstance);
         });
@@ -2646,7 +2646,7 @@ Compute.prototype.getSubnetworksStream = common.paginator.streamify(
  * });
  */
 Compute.prototype.getVMs = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -2666,7 +2666,7 @@ Compute.prototype.getVMs = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -2674,14 +2674,14 @@ Compute.prototype.getVMs = function(options, callback) {
         });
       }
 
-      var zones = resp.items || {};
+      let zones = resp.items || {};
 
-      var vms = Object.keys(zones).reduce(function(acc, zoneName) {
-        var zone = self.zone(zoneName.replace('zones/', ''));
-        var instances = zones[zoneName].instances || [];
+      let vms = Object.keys(zones).reduce(function(acc, zoneName) {
+        let zone = self.zone(zoneName.replace('zones/', ''));
+        let instances = zones[zoneName].instances || [];
 
         instances.forEach(function(instance) {
-          var vmInstance = zone.vm(instance.name);
+          let vmInstance = zone.vm(instance.name);
           vmInstance.metadata = instance;
           acc.push(vmInstance);
         });
@@ -2777,7 +2777,7 @@ Compute.prototype.getVMsStream = common.paginator.streamify('getVMs');
  * });
  */
 Compute.prototype.getZones = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -2795,7 +2795,7 @@ Compute.prototype.getZones = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -2803,8 +2803,8 @@ Compute.prototype.getZones = function(options, callback) {
         });
       }
 
-      var zones = resp.items.map(function(zone) {
-        var zoneInstance = self.zone(zone.name);
+      let zones = resp.items.map(function(zone) {
+        let zoneInstance = self.zone(zone.name);
         zoneInstance.metadata = zone;
         return zoneInstance;
       });
@@ -3012,8 +3012,8 @@ Compute.prototype.zone = function(name) {
 Compute.prototype.execAfterOperation_ = function(callback) {
   return function(err) {
     // arguments = [..., op, apiResponse]
-    var operation = arguments[arguments.length - 2];
-    var apiResponse = arguments[arguments.length - 1];
+    let operation = arguments[arguments.length - 2];
+    let apiResponse = arguments[arguments.length - 1];
 
     if (err) {
       callback(err, apiResponse);
diff --git a/src/instance-group.js b/src/instance-group.js
index bcaa45dd..f444a112 100644
--- a/src/instance-group.js
+++ b/src/instance-group.js
@@ -16,11 +16,11 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var is = require('is');
-var util = require('util');
+let arrify = require('arrify');
+let common = require('@google-cloud/common');
+let extend = require('extend');
+let is = require('is');
+let util = require('util');
 
 /**
  * You can create and manage groups of virtual machine instances so that you
@@ -40,7 +40,7 @@ var util = require('util');
  * const instanceGroup = zone.instanceGroup('web-servers');
  */
 function InstanceGroup(zone, name) {
-  var methods = {
+  let methods = {
     /**
      * Create an instance group.
      *
@@ -249,7 +249,7 @@ InstanceGroup.formatPorts_ = function(ports) {
  * });
  */
 InstanceGroup.prototype.add = function(vms, callback) {
-  var self = this;
+  let self = this;
 
   this.request(
     {
@@ -269,7 +269,7 @@ InstanceGroup.prototype.add = function(vms, callback) {
         return;
       }
 
-      var operation = self.zone.operation(resp.name);
+      let operation = self.zone.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, operation, resp);
@@ -308,7 +308,7 @@ InstanceGroup.prototype.add = function(vms, callback) {
  * });
  */
 InstanceGroup.prototype.delete = function(callback) {
-  var self = this;
+  let self = this;
 
   callback = callback || common.util.noop;
 
@@ -318,7 +318,7 @@ InstanceGroup.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = self.zone.operation(resp.name);
+    let operation = self.zone.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
@@ -384,7 +384,7 @@ InstanceGroup.prototype.delete = function(callback) {
  * });
  */
 InstanceGroup.prototype.getVMs = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -393,7 +393,7 @@ InstanceGroup.prototype.getVMs = function(options, callback) {
 
   options = options || {};
 
-  var body;
+  let body;
 
   if (options.running) {
     body = {
@@ -414,7 +414,7 @@ InstanceGroup.prototype.getVMs = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -422,8 +422,8 @@ InstanceGroup.prototype.getVMs = function(options, callback) {
         });
       }
 
-      var vms = arrify(resp.items).map(function(vm) {
-        var vmInstance = self.zone.vm(vm.instance);
+      let vms = arrify(resp.items).map(function(vm) {
+        let vmInstance = self.zone.vm(vm.instance);
         vmInstance.metadata = vm;
         return vmInstance;
       });
@@ -505,7 +505,7 @@ InstanceGroup.prototype.getVMsStream = common.paginator.streamify('getVMs');
  * });
  */
 InstanceGroup.prototype.remove = function(vms, callback) {
-  var self = this;
+  let self = this;
 
   this.request(
     {
@@ -525,7 +525,7 @@ InstanceGroup.prototype.remove = function(vms, callback) {
         return;
       }
 
-      var operation = self.zone.operation(resp.name);
+      let operation = self.zone.operation(resp.name);
       operation.metadata = resp;
 
       callback(err, operation, resp);
@@ -571,7 +571,7 @@ InstanceGroup.prototype.remove = function(vms, callback) {
  * });
  */
 InstanceGroup.prototype.setPorts = function(ports, callback) {
-  var self = this;
+  let self = this;
 
   callback = callback || common.util.noop;
 
@@ -589,7 +589,7 @@ InstanceGroup.prototype.setPorts = function(ports, callback) {
         return;
       }
 
-      var operation = self.zone.operation(resp.name);
+      let operation = self.zone.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, operation, resp);
diff --git a/src/machine-type.js b/src/machine-type.js
index 30801a3d..bbd2587e 100644
--- a/src/machine-type.js
+++ b/src/machine-type.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /**
  * A MachineType object allows you to interact with a Google Compute Engine
@@ -37,7 +37,7 @@ var util = require('util');
  * const machineType = zone.machineType('g1-small');
  */
 function MachineType(zone, name) {
-  var methods = {
+  let methods = {
     /**
      * Check if the machine type exists.
      *
diff --git a/src/network.js b/src/network.js
index 3789c2b2..35ed4999 100644
--- a/src/network.js
+++ b/src/network.js
@@ -16,11 +16,11 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var format = require('string-format-obj');
-var is = require('is');
-var util = require('util');
+let common = require('@google-cloud/common');
+let extend = require('extend');
+let format = require('string-format-obj');
+let is = require('is');
+let util = require('util');
 
 /**
  * A Network object allows you to interact with a Google Compute Engine network.
@@ -38,7 +38,7 @@ var util = require('util');
  * const network = compute.network('network-name');
  */
 function Network(compute, name) {
-  var methods = {
+  let methods = {
     /**
      * Create a network.
      *
@@ -331,7 +331,7 @@ Network.prototype.createSubnetwork = function(name, config, callback) {
     network: this.formattedName,
   });
 
-  var region = config.region;
+  let region = config.region;
 
   if (is.string(region)) {
     region = this.compute.region(region);
@@ -481,7 +481,7 @@ Network.prototype.getSubnetworksStream = function(options) {
  * });
  */
 Network.prototype.delete = function(callback) {
-  var compute = this.compute;
+  let compute = this.compute;
 
   callback = callback || common.util.noop;
 
@@ -491,7 +491,7 @@ Network.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = compute.operation(resp.name);
+    let operation = compute.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
@@ -512,7 +512,7 @@ Network.prototype.delete = function(callback) {
  * const firewall = network.firewall('firewall-name');
  */
 Network.prototype.firewall = function(name) {
-  var firewall = this.compute.firewall(name);
+  let firewall = this.compute.firewall(name);
 
   firewall.metadata = {
     network: this.formattedName,
diff --git a/src/operation.js b/src/operation.js
index abbf4c99..4014ee6e 100644
--- a/src/operation.js
+++ b/src/operation.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /**
  * An Operation object allows you to interact with a Google Compute Engine
@@ -87,9 +87,9 @@ var util = require('util');
  * operation.removeAllListeners();
  */
 function Operation(scope, name) {
-  var isCompute = scope.constructor.name === 'Compute';
+  let isCompute = scope.constructor.name === 'Compute';
 
-  var methods = {
+  let methods = {
     /**
      * Delete the operation.
      *
@@ -219,11 +219,11 @@ util.inherits(Operation, common.Operation);
  * });
  */
 Operation.prototype.getMetadata = function(callback) {
-  var self = this;
+  let self = this;
 
   callback = callback || common.util.noop;
 
-  var getMetadata = common.ServiceObject.prototype.getMetadata;
+  let getMetadata = common.ServiceObject.prototype.getMetadata;
 
   getMetadata.call(this, function(err, apiResponse) {
     // An Operation entity contains a property named `error`. This makes
@@ -231,7 +231,7 @@ Operation.prototype.getMetadata = function(callback) {
     // this callback. We have to make sure this isn't a false error by seeing if
     // the response body contains a property that wouldn't exist on a failed API
     // request (`name`).
-    var requestFailed = err && (!apiResponse || apiResponse.name !== self.name);
+    let requestFailed = err && (!apiResponse || apiResponse.name !== self.name);
 
     if (requestFailed) {
       callback(err, null, apiResponse);
@@ -254,12 +254,12 @@ Operation.prototype.getMetadata = function(callback) {
  * @private
  */
 Operation.prototype.poll_ = function(callback) {
-  var self = this;
+  let self = this;
 
   this.getMetadata(function(err, metadata, apiResponse) {
     // Parsing the response body will automatically create an ApiError object if
     // the operation failed.
-    var parsedHttpRespBody = common.util.parseHttpRespBody(apiResponse);
+    let parsedHttpRespBody = common.util.parseHttpRespBody(apiResponse);
     err = err || parsedHttpRespBody.err;
 
     if (err) {
diff --git a/src/project.js b/src/project.js
index df44b73e..b334125b 100644
--- a/src/project.js
+++ b/src/project.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /**
  * A Project object allows you to interact with your Google Compute Engine
@@ -41,7 +41,7 @@ function Project(compute) {
    */
   this.id = compute.projectId;
 
-  var methods = {
+  let methods = {
     /**
      * Get a Project object.
      *
diff --git a/src/region.js b/src/region.js
index c75c555e..16a5b61b 100644
--- a/src/region.js
+++ b/src/region.js
@@ -16,16 +16,16 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var is = require('is');
-var util = require('util');
+let common = require('@google-cloud/common');
+let extend = require('extend');
+let is = require('is');
+let util = require('util');
 
-var Address = require('./address.js');
-var Network = require('./network.js');
-var Operation = require('./operation.js');
-var Rule = require('./rule.js');
-var Subnetwork = require('./subnetwork.js');
+let Address = require('./address.js');
+let Network = require('./network.js');
+let Operation = require('./operation.js');
+let Rule = require('./rule.js');
+let Subnetwork = require('./subnetwork.js');
 
 /**
  * A Region object allows you to interact with a Google Compute Engine region.
@@ -43,7 +43,7 @@ var Subnetwork = require('./subnetwork.js');
  * const region = compute.region('us-central1');
  */
 function Region(compute, name) {
-  var methods = {
+  let methods = {
     /**
      * Check if the region exists.
      *
@@ -214,7 +214,7 @@ Region.prototype.address = function(name) {
  * });
  */
 Region.prototype.createAddress = function(name, options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -235,9 +235,9 @@ Region.prototype.createAddress = function(name, options, callback) {
         return;
       }
 
-      var address = self.address(name);
+      let address = self.address(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, address, operation, resp);
@@ -298,9 +298,9 @@ Region.prototype.createAddress = function(name, options, callback) {
  * });
  */
 Region.prototype.createSubnetwork = function(name, config, callback) {
-  var self = this;
+  let self = this;
 
-  var body = extend({}, config, {
+  let body = extend({}, config, {
     name: name,
   });
 
@@ -325,9 +325,9 @@ Region.prototype.createSubnetwork = function(name, config, callback) {
         return;
       }
 
-      var subnetwork = self.subnetwork(name);
+      let subnetwork = self.subnetwork(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, subnetwork, operation, resp);
@@ -458,7 +458,7 @@ Region.prototype.createRule = function(name, config, callback) {
  * });
  */
 Region.prototype.getAddresses = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -478,7 +478,7 @@ Region.prototype.getAddresses = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -486,8 +486,8 @@ Region.prototype.getAddresses = function(options, callback) {
         });
       }
 
-      var addresses = (resp.items || []).map(function(address) {
-        var addressInstance = self.address(address.name);
+      let addresses = (resp.items || []).map(function(address) {
+        let addressInstance = self.address(address.name);
         addressInstance.metadata = address;
         return addressInstance;
       });
@@ -590,7 +590,7 @@ Region.prototype.getAddressesStream = common.paginator.streamify(
  * });
  */
 Region.prototype.getOperations = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -610,7 +610,7 @@ Region.prototype.getOperations = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -618,8 +618,8 @@ Region.prototype.getOperations = function(options, callback) {
         });
       }
 
-      var operations = (resp.items || []).map(function(operation) {
-        var operationInstance = self.operation(operation.name);
+      let operations = (resp.items || []).map(function(operation) {
+        let operationInstance = self.operation(operation.name);
         operationInstance.metadata = operation;
         return operationInstance;
       });
@@ -721,7 +721,7 @@ Region.prototype.getOperationsStream = common.paginator.streamify(
  * });
  */
 Region.prototype.getRules = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -741,7 +741,7 @@ Region.prototype.getRules = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -749,8 +749,8 @@ Region.prototype.getRules = function(options, callback) {
         });
       }
 
-      var rules = (resp.items || []).map(function(rule) {
-        var ruleInstance = self.rule(rule.name);
+      let rules = (resp.items || []).map(function(rule) {
+        let ruleInstance = self.rule(rule.name);
         ruleInstance.metadata = rule;
         return ruleInstance;
       });
@@ -851,7 +851,7 @@ Region.prototype.getRulesStream = common.paginator.streamify('getRules');
  * });
  */
 Region.prototype.getSubnetworks = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -871,7 +871,7 @@ Region.prototype.getSubnetworks = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -879,8 +879,8 @@ Region.prototype.getSubnetworks = function(options, callback) {
         });
       }
 
-      var subnetworks = (resp.items || []).map(function(subnetwork) {
-        var subnetworkInstance = self.subnetwork(subnetwork.name);
+      let subnetworks = (resp.items || []).map(function(subnetwork) {
+        let subnetworkInstance = self.subnetwork(subnetwork.name);
         subnetworkInstance.metadata = subnetwork;
         return subnetworkInstance;
       });
diff --git a/src/rule.js b/src/rule.js
index d73897e8..b56e07d0 100644
--- a/src/rule.js
+++ b/src/rule.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /**
  * Forwarding rules work in conjunction with target pools and target instances
@@ -49,9 +49,9 @@ var util = require('util');
  * const rule = region.rule('rule-name');
  */
 function Rule(scope, name) {
-  var isGlobalRule = scope.constructor.name === 'Compute';
+  let isGlobalRule = scope.constructor.name === 'Compute';
 
-  var methods = {
+  let methods = {
     /**
      * Create a forwarding rule.
      *
@@ -234,7 +234,7 @@ util.inherits(Rule, common.ServiceObject);
 Rule.prototype.delete = function(callback) {
   callback = callback || common.util.noop;
 
-  var scope = this.scope;
+  let scope = this.scope;
 
   common.ServiceObject.prototype.delete.call(this, function(err, resp) {
     if (err) {
@@ -242,7 +242,7 @@ Rule.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = scope.operation(resp.name);
+    let operation = scope.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
@@ -285,7 +285,7 @@ Rule.prototype.delete = function(callback) {
 Rule.prototype.setTarget = function(target, callback) {
   callback = callback || common.util.noop;
 
-  var scope = this.scope;
+  let scope = this.scope;
 
   this.request(
     {
@@ -301,7 +301,7 @@ Rule.prototype.setTarget = function(target, callback) {
         return;
       }
 
-      var operation = scope.operation(resp.name);
+      let operation = scope.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, operation, resp);
diff --git a/src/service.js b/src/service.js
index a8e04a19..50f15bde 100644
--- a/src/service.js
+++ b/src/service.js
@@ -16,11 +16,11 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var common = require('@google-cloud/common');
-var format = require('string-format-obj');
-var is = require('is');
-var util = require('util');
+let arrify = require('arrify');
+let common = require('@google-cloud/common');
+let format = require('string-format-obj');
+let is = require('is');
+let util = require('util');
 
 /**
  * An HTTP(S) load balancing backend service is a centralized service for
@@ -44,7 +44,7 @@ var util = require('util');
  * const service = const.service('service-name');
  */
 function Service(compute, name) {
-  var methods = {
+  let methods = {
     /**
      * Create a backend service.
      *
@@ -231,7 +231,7 @@ util.inherits(Service, common.ServiceObject);
  * });
  */
 Service.prototype.delete = function(callback) {
-  var compute = this.compute;
+  let compute = this.compute;
 
   callback = callback || common.util.noop;
 
@@ -241,7 +241,7 @@ Service.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = compute.operation(resp.name);
+    let operation = compute.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
@@ -360,7 +360,7 @@ Service.prototype.getHealth = function(group, callback) {
  * });
  */
 Service.prototype.setMetadata = function(metadata, callback) {
-  var compute = this.compute;
+  let compute = this.compute;
 
   callback = callback || common.util.noop;
 
@@ -376,7 +376,7 @@ Service.prototype.setMetadata = function(metadata, callback) {
         return;
       }
 
-      var operation = compute.operation(resp.name);
+      let operation = compute.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, operation, resp);
diff --git a/src/snapshot.js b/src/snapshot.js
index bccfa9cd..acd2de77 100644
--- a/src/snapshot.js
+++ b/src/snapshot.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /**
  * A Snapshot object allows you to interact with a Google Compute Engine
@@ -43,9 +43,9 @@ var util = require('util');
  * const snapshot = disk.snapshot('disk-snapshot-name');
  */
 function Snapshot(scope, name) {
-  var isDisk = scope.constructor.name === 'Disk';
+  let isDisk = scope.constructor.name === 'Disk';
 
-  var methods = {
+  let methods = {
     /**
      * Check if the snapshot exists.
      *
@@ -127,7 +127,7 @@ function Snapshot(scope, name) {
     getMetadata: true,
   };
 
-  var config = {
+  let config = {
     parent: scope,
     baseUrl:
       'https://www.googleapis.com/compute/v1/projects/{{projectId}}/global/snapshots',
@@ -223,7 +223,7 @@ util.inherits(Snapshot, common.ServiceObject);
 Snapshot.prototype.delete = function(callback) {
   callback = callback || common.util.noop;
 
-  var compute = this.compute;
+  let compute = this.compute;
 
   common.ServiceObject.prototype.delete.call(this, function(err, resp) {
     if (err) {
@@ -231,7 +231,7 @@ Snapshot.prototype.delete = function(callback) {
       return;
     }
 
-    var operation = compute.operation(resp.name);
+    let operation = compute.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
diff --git a/src/subnetwork.js b/src/subnetwork.js
index 7ab996a5..65ea509f 100644
--- a/src/subnetwork.js
+++ b/src/subnetwork.js
@@ -16,8 +16,8 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var util = require('util');
+let common = require('@google-cloud/common');
+let util = require('util');
 
 /**
  * An Subnetwork object allows you to interact with a Google Compute Engine
@@ -49,7 +49,7 @@ function Subnetwork(region, name) {
    */
   this.region = region;
 
-  var methods = {
+  let methods = {
     /**
      * Create a subnetwork.
      *
@@ -221,7 +221,7 @@ util.inherits(Subnetwork, common.ServiceObject);
 Subnetwork.prototype.delete = function(callback) {
   callback = callback || common.util.noop;
 
-  var region = this.region;
+  let region = this.region;
 
   this.request(
     {
@@ -234,7 +234,7 @@ Subnetwork.prototype.delete = function(callback) {
         return;
       }
 
-      var operation = region.operation(resp.name);
+      let operation = region.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, operation, resp);
diff --git a/src/vm.js b/src/vm.js
index 41d15898..db5e0562 100644
--- a/src/vm.js
+++ b/src/vm.js
@@ -16,14 +16,14 @@
 
 'use strict';
 
-var common = require('@google-cloud/common');
-var createErrorClass = require('create-error-class');
-var extend = require('extend');
-var format = require('string-format-obj');
-var is = require('is');
-var util = require('util');
+let common = require('@google-cloud/common');
+let createErrorClass = require('create-error-class');
+let extend = require('extend');
+let format = require('string-format-obj');
+let is = require('is');
+let util = require('util');
 
-var Disk = require('./disk.js');
+let Disk = require('./disk.js');
 
 /**
  * Custom error type for errors related to detaching a disk.
@@ -33,7 +33,7 @@ var Disk = require('./disk.js');
  * @param {string} message - Custom error message.
  * @returns {Error}
  */
-var DetachDiskError = createErrorClass('DetachDiskError');
+let DetachDiskError = createErrorClass('DetachDiskError');
 
 /**
  * Custom error type for when `waitFor()` does not return a status in a timely
@@ -44,14 +44,14 @@ var DetachDiskError = createErrorClass('DetachDiskError');
  * @param {string} message - Custom error message.
  * @returns {Error}
  */
-var WaitForTimeoutError = createErrorClass('WaitForTimeoutError');
+let WaitForTimeoutError = createErrorClass('WaitForTimeoutError');
 
 /**
  * The statuses that a VM can be in.
  *
  * @private
  */
-var VALID_STATUSES = [
+let VALID_STATUSES = [
   'PROVISIONING',
   'STAGING',
   'RUNNING',
@@ -66,7 +66,7 @@ var VALID_STATUSES = [
  *
  * @private
  */
-var WAIT_FOR_POLLING_INTERVAL_MS = 2000;
+let WAIT_FOR_POLLING_INTERVAL_MS = 2000;
 
 /**
  * An Instance object allows you to interact with a Google Compute Engine
@@ -108,7 +108,7 @@ function VM(zone, name) {
     name: this.name,
   });
 
-  var methods = {
+  let methods = {
     /**
      * Create a virtual machine.
      *
@@ -313,7 +313,7 @@ VM.prototype.attachDisk = function(disk, options, callback) {
     options = {};
   }
 
-  var body = extend(
+  let body = extend(
     {
       // Default the deviceName to the name of the disk, like the Console does.
       deviceName: disk.name,
@@ -415,7 +415,7 @@ VM.prototype.delete = function(callback) {
  * });
  */
 VM.prototype.detachDisk = function(disk, callback) {
-  var self = this;
+  let self = this;
 
   if (!(disk instanceof Disk)) {
     throw new Error('A Disk object must be provided.');
@@ -427,20 +427,20 @@ VM.prototype.detachDisk = function(disk, callback) {
       return;
     }
 
-    var diskName = common.util.replaceProjectIdToken(
+    let diskName = common.util.replaceProjectIdToken(
       disk.formattedName,
       self.zone.compute.authClient.projectId
     );
 
-    var deviceName;
-    var baseUrl = 'https://www.googleapis.com/compute/v1/';
-    var disks = metadata.disks || [];
+    let deviceName;
+    let baseUrl = 'https://www.googleapis.com/compute/v1/';
+    let disks = metadata.disks || [];
 
     // Try to find the deviceName by matching the source of the attached disks
     // to the name of the disk provided by the user.
-    for (var i = 0; !deviceName && i < disks.length; i++) {
-      var attachedDisk = disks[i];
-      var source = attachedDisk.source.replace(baseUrl, '');
+    for (let i = 0; !deviceName && i < disks.length; i++) {
+      let attachedDisk = disks[i];
+      let source = attachedDisk.source.replace(baseUrl, '');
 
       if (source === diskName) {
         deviceName = attachedDisk.deviceName;
@@ -499,14 +499,14 @@ VM.prototype.getSerialPortOutput = function(port, callback) {
     port = 1;
   }
 
-  var reqOpts = {
+  let reqOpts = {
     uri: '/serialPort',
     qs: {
       port: port,
     },
   };
 
-  var request = common.ServiceObject.prototype.request;
+  let request = common.ServiceObject.prototype.request;
 
   request.call(this, reqOpts, function(err, resp) {
     if (err) {
@@ -658,8 +658,8 @@ VM.prototype.reset = function(callback) {
  * });
  */
 VM.prototype.resize = function(machineType, options, callback) {
-  var self = this;
-  var compute = this.zone.parent;
+  let self = this;
+  let compute = this.zone.parent;
 
   if (is.fn(options)) {
     callback = options;
@@ -668,7 +668,7 @@ VM.prototype.resize = function(machineType, options, callback) {
 
   options = options || {};
 
-  var isPartialMachineType = machineType.indexOf('/') === -1;
+  let isPartialMachineType = machineType.indexOf('/') === -1;
 
   if (isPartialMachineType) {
     machineType = format('zones/{zoneName}/machineTypes/{machineType}', {
@@ -752,7 +752,7 @@ VM.prototype.resize = function(machineType, options, callback) {
  * });
  */
 VM.prototype.setMetadata = function(metadata, callback) {
-  var self = this;
+  let self = this;
 
   callback = callback || common.util.noop;
 
@@ -762,12 +762,12 @@ VM.prototype.setMetadata = function(metadata, callback) {
       return;
     }
 
-    var newMetadata = {
+    let newMetadata = {
       fingerprint: currentMetadata.metadata.fingerprint,
       items: [],
     };
 
-    for (var prop in metadata) {
+    for (let prop in metadata) {
       if (metadata.hasOwnProperty(prop)) {
         newMetadata.items.push({
           key: prop,
@@ -832,7 +832,7 @@ VM.prototype.setMetadata = function(metadata, callback) {
  * });
  */
 VM.prototype.setTags = function(tags, fingerprint, callback) {
-  var body = {
+  let body = {
     items: tags,
     fingerprint: fingerprint,
   };
@@ -995,7 +995,7 @@ VM.prototype.waitFor = function(status, options, callback) {
 
   // The timeout should default to five minutes, be less than or equal to 10
   // minutes, and be greater than or equal to 0 seconds.
-  var timeout = 300;
+  let timeout = 300;
 
   if (is.number(options.timeout)) {
     timeout = Math.min(Math.max(options.timeout, 0), 600);
@@ -1028,16 +1028,16 @@ VM.prototype.waitFor = function(status, options, callback) {
  * @private
  */
 VM.prototype.startPolling_ = function() {
-  var self = this;
+  let self = this;
 
   if (!this.hasActiveWaiters) {
     return;
   }
 
   this.getMetadata(function(err, metadata) {
-    var now = new Date() / 1000;
+    let now = new Date() / 1000;
 
-    var waitersToRemove = self.waiters.filter(function(waiter) {
+    let waitersToRemove = self.waiters.filter(function(waiter) {
       if (err) {
         waiter.callback(err);
         return true;
@@ -1049,7 +1049,7 @@ VM.prototype.startPolling_ = function() {
       }
 
       if (now - waiter.startTime >= waiter.timeout) {
-        var waitForTimeoutError = new WaitForTimeoutError(
+        let waitForTimeoutError = new WaitForTimeoutError(
           [
             'waitFor timed out waiting for VM ' + self.name,
             'to be in status: ' + waiter.status,
@@ -1090,9 +1090,9 @@ VM.prototype.startPolling_ = function() {
  * @param {function} callback - The callback function.
  */
 VM.prototype.request = function(reqOpts, callback) {
-  var zone = this.zone;
+  let zone = this.zone;
 
-  var request = common.ServiceObject.prototype.request;
+  let request = common.ServiceObject.prototype.request;
 
   request.call(this, reqOpts, function(err, resp) {
     if (err) {
@@ -1100,7 +1100,7 @@ VM.prototype.request = function(reqOpts, callback) {
       return;
     }
 
-    var operation = zone.operation(resp.name);
+    let operation = zone.operation(resp.name);
     operation.metadata = resp;
 
     callback(null, operation, resp);
diff --git a/src/zone.js b/src/zone.js
index 3b0b1411..f815c73b 100644
--- a/src/zone.js
+++ b/src/zone.js
@@ -16,21 +16,21 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var async = require('async');
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var format = require('string-format-obj');
-var gceImages = require('gce-images');
-var is = require('is');
-var util = require('util');
-
-var Autoscaler = require('./autoscaler.js');
-var Disk = require('./disk.js');
-var InstanceGroup = require('./instance-group.js');
-var MachineType = require('./machine-type.js');
-var Operation = require('./operation.js');
-var VM = require('./vm.js');
+let arrify = require('arrify');
+let async = require('async');
+let common = require('@google-cloud/common');
+let extend = require('extend');
+let format = require('string-format-obj');
+let gceImages = require('gce-images');
+let is = require('is');
+let util = require('util');
+
+let Autoscaler = require('./autoscaler.js');
+let Disk = require('./disk.js');
+let InstanceGroup = require('./instance-group.js');
+let MachineType = require('./machine-type.js');
+let Operation = require('./operation.js');
+let VM = require('./vm.js');
 
 /**
  * A Zone object allows you to interact with a Google Compute Engine zone.
@@ -48,7 +48,7 @@ var VM = require('./vm.js');
  * const zone = compute.zone('us-central1-a');
  */
 function Zone(compute, name) {
-  var methods = {
+  let methods = {
     /**
      * Check if the zone exists.
      *
@@ -247,13 +247,13 @@ Zone.prototype.autoscaler = function(name) {
  * });
  */
 Zone.prototype.createAutoscaler = function(name, config, callback) {
-  var self = this;
+  let self = this;
 
   if (!config.target) {
     throw new Error('Cannot create an autoscaler without a target.');
   }
 
-  var json = extend(true, {}, config, {
+  let json = extend(true, {}, config, {
     name: name,
     autoscalingPolicy: {},
   });
@@ -310,9 +310,9 @@ Zone.prototype.createAutoscaler = function(name, config, callback) {
         return;
       }
 
-      var autoscaler = self.autoscaler(name);
+      let autoscaler = self.autoscaler(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, autoscaler, operation, resp);
@@ -379,10 +379,10 @@ Zone.prototype.createAutoscaler = function(name, config, callback) {
  * });
  */
 Zone.prototype.createDisk = function(name, config, callback) {
-  var self = this;
+  let self = this;
 
-  var query = {};
-  var body = extend({}, config, {
+  let query = {};
+  let body = extend({}, config, {
     name: name,
   });
 
@@ -419,9 +419,9 @@ Zone.prototype.createDisk = function(name, config, callback) {
         return;
       }
 
-      var disk = self.disk(name);
+      let disk = self.disk(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, disk, operation, resp);
@@ -472,14 +472,14 @@ Zone.prototype.createDisk = function(name, config, callback) {
  * });
  */
 Zone.prototype.createInstanceGroup = function(name, options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
     options = {};
   }
 
-  var body = extend({}, options, {
+  let body = extend({}, options, {
     name: name,
   });
 
@@ -500,9 +500,9 @@ Zone.prototype.createInstanceGroup = function(name, options, callback) {
         return;
       }
 
-      var instanceGroup = self.instanceGroup(name);
+      let instanceGroup = self.instanceGroup(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, instanceGroup, operation, resp);
@@ -617,9 +617,9 @@ Zone.prototype.createInstanceGroup = function(name, options, callback) {
  * });
  */
 Zone.prototype.createVM = function(name, config, callback) {
-  var self = this;
+  let self = this;
 
-  var body = extend(
+  let body = extend(
     {
       name: name,
       machineType: 'n1-standard-1',
@@ -650,7 +650,7 @@ Zone.prototype.createVM = function(name, config, callback) {
     // We will add tags to the created instance (http-server and/or
     // https-server), and create the appropriate firewall rules to allow
     // connections on the necessary ports to these tags.
-    var createFirewallMethods = [];
+    let createFirewallMethods = [];
 
     body.networkInterfaces[0].accessConfigs = [
       {
@@ -729,9 +729,9 @@ Zone.prototype.createVM = function(name, config, callback) {
         return;
       }
 
-      var vm = self.vm(name);
+      let vm = self.vm(name);
 
-      var operation = self.operation(resp.name);
+      let operation = self.operation(resp.name);
       operation.metadata = resp;
 
       callback(null, vm, operation, resp);
@@ -817,7 +817,7 @@ Zone.prototype.disk = function(name) {
  * });
  */
 Zone.prototype.getAutoscalers = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -837,7 +837,7 @@ Zone.prototype.getAutoscalers = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -845,8 +845,8 @@ Zone.prototype.getAutoscalers = function(options, callback) {
         });
       }
 
-      var autoscalers = arrify(resp.items).map(function(autoscaler) {
-        var autoscalerInstance = self.autoscaler(autoscaler.name);
+      let autoscalers = arrify(resp.items).map(function(autoscaler) {
+        let autoscalerInstance = self.autoscaler(autoscaler.name);
         autoscalerInstance.metadata = autoscaler;
 
         return autoscalerInstance;
@@ -949,7 +949,7 @@ Zone.prototype.getAutoscalersStream = common.paginator.streamify(
  * });
  */
 Zone.prototype.getDisks = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -969,7 +969,7 @@ Zone.prototype.getDisks = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -977,8 +977,8 @@ Zone.prototype.getDisks = function(options, callback) {
         });
       }
 
-      var disks = (resp.items || []).map(function(disk) {
-        var diskInstance = self.disk(disk.name);
+      let disks = (resp.items || []).map(function(disk) {
+        let diskInstance = self.disk(disk.name);
         diskInstance.metadata = disk;
         return diskInstance;
       });
@@ -1080,7 +1080,7 @@ Zone.prototype.getDisksStream = common.paginator.streamify('getDisks');
  * });
  */
 Zone.prototype.getInstanceGroups = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1100,7 +1100,7 @@ Zone.prototype.getInstanceGroups = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1108,8 +1108,8 @@ Zone.prototype.getInstanceGroups = function(options, callback) {
         });
       }
 
-      var instanceGroups = (resp.items || []).map(function(instanceGroup) {
-        var instanceGroupInstance = self.instanceGroup(instanceGroup.name);
+      let instanceGroups = (resp.items || []).map(function(instanceGroup) {
+        let instanceGroupInstance = self.instanceGroup(instanceGroup.name);
         instanceGroupInstance.metadata = instanceGroup;
         return instanceGroupInstance;
       });
@@ -1312,7 +1312,7 @@ Zone.prototype.getMachineTypesStream = common.paginator.streamify(
  * });
  */
 Zone.prototype.getOperations = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1332,7 +1332,7 @@ Zone.prototype.getOperations = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1340,8 +1340,8 @@ Zone.prototype.getOperations = function(options, callback) {
         });
       }
 
-      var operations = (resp.items || []).map(function(operation) {
-        var operationInstance = self.operation(operation.name);
+      let operations = (resp.items || []).map(function(operation) {
+        let operationInstance = self.operation(operation.name);
         operationInstance.metadata = operation;
         return operationInstance;
       });
@@ -1441,7 +1441,7 @@ Zone.prototype.getOperationsStream = common.paginator.streamify(
  * });
  */
 Zone.prototype.getVMs = function(options, callback) {
-  var self = this;
+  let self = this;
 
   if (is.fn(options)) {
     callback = options;
@@ -1461,7 +1461,7 @@ Zone.prototype.getVMs = function(options, callback) {
         return;
       }
 
-      var nextQuery = null;
+      let nextQuery = null;
 
       if (resp.nextPageToken) {
         nextQuery = extend({}, options, {
@@ -1469,8 +1469,8 @@ Zone.prototype.getVMs = function(options, callback) {
         });
       }
 
-      var vms = (resp.items || []).map(function(instance) {
-        var vmInstance = self.vm(instance.name);
+      let vms = (resp.items || []).map(function(instance) {
+        let vmInstance = self.vm(instance.name);
         vmInstance.metadata = instance;
         return vmInstance;
       });
diff --git a/system-test/compute.js b/system-test/compute.js
index 82878741..6ae86b22 100644
--- a/system-test/compute.js
+++ b/system-test/compute.js
@@ -16,14 +16,14 @@
 
 'use strict';
 
-var assert = require('assert');
-var async = require('async');
-var concat = require('concat-stream');
-var is = require('is');
-var prop = require('propprop');
-var uuid = require('uuid');
+let assert = require('assert');
+let async = require('async');
+let concat = require('concat-stream');
+let is = require('is');
+let prop = require('propprop');
+let uuid = require('uuid');
 
-var Compute = require('../');
+let Compute = require('../');
 
 describe('Compute', function() {
   // Since the Compute Engine API is rather large and involves long-running
@@ -40,20 +40,20 @@ describe('Compute', function() {
   // deleted. This will also pick up any previously-created objects that were
   // unable to be removed if a prior test run had unexpectedly quit.
 
-  var TESTS_PREFIX = 'gcloud-tests-';
-  var REGION_NAME = 'us-central1';
-  var ZONE_NAME = 'us-central1-a';
+  let TESTS_PREFIX = 'gcloud-tests-';
+  let REGION_NAME = 'us-central1';
+  let ZONE_NAME = 'us-central1-a';
 
-  var compute = new Compute();
-  var region = compute.region(REGION_NAME);
-  var zone = compute.zone(ZONE_NAME);
+  let compute = new Compute();
+  let region = compute.region(REGION_NAME);
+  let zone = compute.zone(ZONE_NAME);
 
   before(deleteAllTestObjects);
   after(deleteAllTestObjects);
 
   describe('addresses', function() {
-    var ADDRESS_NAME = generateName('address');
-    var address = region.address(ADDRESS_NAME);
+    let ADDRESS_NAME = generateName('address');
+    let address = region.address(ADDRESS_NAME);
 
     before(create(address));
 
@@ -74,7 +74,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of addresses in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getAddressesStream()
@@ -94,14 +94,14 @@ describe('Compute', function() {
   });
 
   describe('autoscalers', function() {
-    var AUTOSCALER_NAME = generateName('autoscaler');
-    var autoscaler = zone.autoscaler(AUTOSCALER_NAME);
+    let AUTOSCALER_NAME = generateName('autoscaler');
+    let autoscaler = zone.autoscaler(AUTOSCALER_NAME);
 
-    var NETWORK_NAME = generateName('network');
-    var network = compute.network(NETWORK_NAME);
+    let NETWORK_NAME = generateName('network');
+    let network = compute.network(NETWORK_NAME);
 
-    var INSTANCE_TEMPLATE_NAME = generateName('instance-template');
-    var INSTANCE_GROUP_MANAGER_NAME = generateName('instance-group-manager');
+    let INSTANCE_TEMPLATE_NAME = generateName('instance-template');
+    let INSTANCE_GROUP_MANAGER_NAME = generateName('instance-group-manager');
 
     before(function(done) {
       async.series(
@@ -175,7 +175,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of autoscalers in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getAutoscalersStream()
@@ -190,7 +190,7 @@ describe('Compute', function() {
     });
 
     it('should set & get metadata', function(done) {
-      var description = 'description';
+      let description = 'description';
 
       autoscaler.setMetadata(
         {
@@ -210,8 +210,8 @@ describe('Compute', function() {
   });
 
   describe('disks', function() {
-    var DISK_NAME = generateName('disk');
-    var disk = zone.disk(DISK_NAME);
+    let DISK_NAME = generateName('disk');
+    let disk = zone.disk(DISK_NAME);
 
     before(create(disk, {os: 'ubuntu'}));
 
@@ -232,7 +232,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of disks in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getDisksStream()
@@ -263,20 +263,20 @@ describe('Compute', function() {
     });
 
     it('should run operation as a promise', function() {
-      var snapshot = disk.snapshot(generateName('snapshot'));
+      let snapshot = disk.snapshot(generateName('snapshot'));
 
       return snapshot.create().then(function(response) {
-        var operation = response[1];
+        let operation = response[1];
         return operation.promise();
       });
     });
   });
 
   describe('firewalls', function() {
-    var FIREWALL_NAME = generateName('firewall');
-    var firewall = compute.firewall(FIREWALL_NAME);
+    let FIREWALL_NAME = generateName('firewall');
+    let firewall = compute.firewall(FIREWALL_NAME);
 
-    var CONFIG = {
+    let CONFIG = {
       protocols: {
         tcp: [3000],
         icmp: true, // This should open all ports on this protocol
@@ -286,7 +286,7 @@ describe('Compute', function() {
       ranges: ['0.0.0.0/0'],
     };
 
-    var expectedMetadata = {
+    let expectedMetadata = {
       allowed: [
         {
           IPProtocol: 'tcp',
@@ -323,7 +323,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of firewalls in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getFirewallsStream()
@@ -339,10 +339,10 @@ describe('Compute', function() {
   });
 
   describe('health checks', function() {
-    var HEALTH_CHECK_NAME = generateName('health-check');
-    var healthCheck = compute.healthCheck(HEALTH_CHECK_NAME);
+    let HEALTH_CHECK_NAME = generateName('health-check');
+    let healthCheck = compute.healthCheck(HEALTH_CHECK_NAME);
 
-    var OPTIONS = {
+    let OPTIONS = {
       description: 'A health check.',
       interval: 50,
       timeout: 25,
@@ -363,7 +363,7 @@ describe('Compute', function() {
     });
 
     it('should set metadata', function(done) {
-      var description = 'The best description. Possibly ever.';
+      let description = 'The best description. Possibly ever.';
 
       healthCheck.setMetadata(
         {
@@ -398,7 +398,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of health checks in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getHealthChecksStream()
@@ -414,12 +414,12 @@ describe('Compute', function() {
   });
 
   describe('health checks (https)', function() {
-    var HEALTH_CHECK_NAME = generateName('health-check');
-    var healthCheck = compute.healthCheck(HEALTH_CHECK_NAME, {
+    let HEALTH_CHECK_NAME = generateName('health-check');
+    let healthCheck = compute.healthCheck(HEALTH_CHECK_NAME, {
       https: true,
     });
 
-    var OPTIONS = {
+    let OPTIONS = {
       description: 'A health check.',
       interval: 50,
       timeout: 25,
@@ -440,7 +440,7 @@ describe('Compute', function() {
     });
 
     it('should set metadata', function(done) {
-      var description = 'The best description. Possibly ever.';
+      let description = 'The best description. Possibly ever.';
 
       healthCheck.setMetadata(
         {
@@ -475,7 +475,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of health checks in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getHealthChecksStream({https: true})
@@ -491,8 +491,8 @@ describe('Compute', function() {
   });
 
   describe('images', function() {
-    var DISK = zone.disk(generateName('disk'));
-    var IMAGE = compute.image(generateName('image'));
+    let DISK = zone.disk(generateName('disk'));
+    let IMAGE = compute.image(generateName('image'));
 
     before(create(DISK, {os: 'ubuntu'}));
     before(create(IMAGE, DISK));
@@ -514,7 +514,7 @@ describe('Compute', function() {
     });
 
     it('should list images in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getImagesStream()
@@ -530,10 +530,10 @@ describe('Compute', function() {
   });
 
   describe('instance groups', function() {
-    var INSTANCE_GROUP_NAME = generateName('instance-group');
-    var instanceGroup = zone.instanceGroup(INSTANCE_GROUP_NAME);
+    let INSTANCE_GROUP_NAME = generateName('instance-group');
+    let instanceGroup = zone.instanceGroup(INSTANCE_GROUP_NAME);
 
-    var OPTIONS = {
+    let OPTIONS = {
       description: 'new instance group',
       ports: {
         http: 80,
@@ -568,7 +568,7 @@ describe('Compute', function() {
     });
 
     it('should list project instance groups in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getInstanceGroupsStream()
@@ -591,7 +591,7 @@ describe('Compute', function() {
     });
 
     it('should list zonal instance groups in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       zone
         .getInstanceGroupsStream()
@@ -606,7 +606,7 @@ describe('Compute', function() {
     });
 
     it('should set named ports', function(done) {
-      var ports = OPTIONS.ports;
+      let ports = OPTIONS.ports;
 
       instanceGroup.setPorts(
         ports,
@@ -628,7 +628,7 @@ describe('Compute', function() {
     });
 
     describe('adding and removing VMs', function() {
-      var vm = zone.vm(generateName('vm'));
+      let vm = zone.vm(generateName('vm'));
 
       before(create(vm, {os: 'ubuntu'}));
 
@@ -640,7 +640,7 @@ describe('Compute', function() {
         instanceGroup.getVMs(function(err, vms) {
           assert.ifError(err);
 
-          var vmNamesInGroup = vms.map(prop('name'));
+          let vmNamesInGroup = vms.map(prop('name'));
           assert(vmNamesInGroup.indexOf(vm.name) > -1);
 
           done();
@@ -653,7 +653,7 @@ describe('Compute', function() {
           .on('error', done)
           .pipe(
             concat(function(vms) {
-              var vmNamesInGroup = vms.map(prop('name'));
+              let vmNamesInGroup = vms.map(prop('name'));
               assert(vmNamesInGroup.indexOf(vm.name) > -1);
 
               done();
@@ -677,7 +677,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of machine types in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getMachineTypesStream()
@@ -715,7 +715,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of machine types in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       zone
         .getMachineTypesStream()
@@ -744,10 +744,10 @@ describe('Compute', function() {
   });
 
   describe('networks', function() {
-    var NETWORK_NAME = generateName('network');
-    var network = compute.network(NETWORK_NAME);
+    let NETWORK_NAME = generateName('network');
+    let network = compute.network(NETWORK_NAME);
 
-    var CONFIG = {
+    let CONFIG = {
       range: '10.240.0.0/16',
     };
 
@@ -770,7 +770,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of networks in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getNetworksStream()
@@ -795,7 +795,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of operations in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getOperationsStream()
@@ -811,7 +811,7 @@ describe('Compute', function() {
   });
 
   describe('project', function() {
-    var project;
+    let project;
 
     beforeEach(function() {
       project = compute.project();
@@ -844,7 +844,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of regions in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getRegionsStream()
@@ -867,7 +867,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of addresses in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       region
         .getOperationsStream()
@@ -890,7 +890,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of operations in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       region
         .getOperationsStream()
@@ -906,19 +906,19 @@ describe('Compute', function() {
   });
 
   describe('rules', function() {
-    var RULE_NAME = generateName('rule');
-    var rule = compute.rule(RULE_NAME);
+    let RULE_NAME = generateName('rule');
+    let rule = compute.rule(RULE_NAME);
 
-    var service = compute.service(generateName('service'));
+    let service = compute.service(generateName('service'));
 
-    var INSTANCE_GROUP_NAME = generateName('instance-group');
-    var HEALTH_CHECK_NAME = generateName('health-check');
+    let INSTANCE_GROUP_NAME = generateName('instance-group');
+    let HEALTH_CHECK_NAME = generateName('health-check');
 
     // To create a rule, we need to also create a TargetHttpProxy and UrlMap.
     // Until they are officially supported by google-cloud-node, we make manual
     // requests to create and delete them.
-    var TARGET_PROXY_NAME = generateName('target-proxy');
-    var URL_MAP_NAME = generateName('url-map');
+    let TARGET_PROXY_NAME = generateName('target-proxy');
+    let URL_MAP_NAME = generateName('url-map');
 
     before(function(done) {
       async.series(
@@ -971,7 +971,7 @@ describe('Compute', function() {
     });
 
     it('should have created the right rule', function(done) {
-      var target = [
+      let target = [
         'https://www.googleapis.com/compute/v1/global/targetHttpProxies/',
         TARGET_PROXY_NAME,
       ].join('');
@@ -992,7 +992,7 @@ describe('Compute', function() {
     });
 
     it('should set a new target', function(done) {
-      var target = [
+      let target = [
         'https://www.googleapis.com/compute/v1/projects/' + compute.projectId,
         '/global/targetHttpProxies/' + TARGET_PROXY_NAME,
       ].join('');
@@ -1019,13 +1019,13 @@ describe('Compute', function() {
   });
 
   describe('rules (regional)', function() {
-    var RULE_NAME = generateName('rule');
-    var rule = region.rule(RULE_NAME);
+    let RULE_NAME = generateName('rule');
+    let rule = region.rule(RULE_NAME);
 
-    var TARGET_INSTANCE_NAME = generateName('target-instance');
+    let TARGET_INSTANCE_NAME = generateName('target-instance');
 
-    var VM_NAME = generateName('vm');
-    var vm = zone.vm(VM_NAME);
+    let VM_NAME = generateName('vm');
+    let vm = zone.vm(VM_NAME);
 
     before(function(done) {
       async.series(
@@ -1059,7 +1059,7 @@ describe('Compute', function() {
     });
 
     it('should have created the right rule', function(done) {
-      var target = [
+      let target = [
         'https://www.googleapis.com/compute/v1/projects/' + compute.projectId,
         '/zones/' + zone.name + '/targetInstances/' + TARGET_INSTANCE_NAME,
       ].join('');
@@ -1081,10 +1081,10 @@ describe('Compute', function() {
   });
 
   describe('services', function() {
-    var service = compute.service(generateName('service'));
+    let service = compute.service(generateName('service'));
 
-    var INSTANCE_GROUP_NAME = generateName('instance-group');
-    var HEALTH_CHECK_NAME = generateName('health-check');
+    let INSTANCE_GROUP_NAME = generateName('instance-group');
+    let HEALTH_CHECK_NAME = generateName('health-check');
 
     before(function(done) {
       createService(service.name, INSTANCE_GROUP_NAME, HEALTH_CHECK_NAME, done);
@@ -1099,7 +1099,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of services in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getServicesStream()
@@ -1128,7 +1128,7 @@ describe('Compute', function() {
     });
 
     it('should set metadata', function(done) {
-      var description = 'The best description. Possibly ever.';
+      let description = 'The best description. Possibly ever.';
 
       service.setMetadata(
         {
@@ -1165,7 +1165,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of snapshots in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getSnapshotsStream()
@@ -1181,17 +1181,17 @@ describe('Compute', function() {
   });
 
   describe('subnetworks', function() {
-    var NETWORK_NAME = generateName('network');
-    var network = compute.network(NETWORK_NAME);
+    let NETWORK_NAME = generateName('network');
+    let network = compute.network(NETWORK_NAME);
 
-    var SUBNETWORK_NAME = generateName('subnetwork');
-    var subnetwork = region.subnetwork(SUBNETWORK_NAME);
+    let SUBNETWORK_NAME = generateName('subnetwork');
+    let subnetwork = region.subnetwork(SUBNETWORK_NAME);
 
-    var NETWORK_CONFIG = {
+    let NETWORK_CONFIG = {
       autoCreateSubnetworks: false,
     };
 
-    var SUBNETWORK_CONFIG = {
+    let SUBNETWORK_CONFIG = {
       network: 'global/networks/' + NETWORK_NAME,
       range: '10.0.1.0/24',
     };
@@ -1223,7 +1223,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of subnetworks in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getSubnetworksStream()
@@ -1246,7 +1246,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of regional subnetworks in stream', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       region
         .getSubnetworksStream()
@@ -1266,8 +1266,8 @@ describe('Compute', function() {
   });
 
   describe('vms', function() {
-    var VM_NAME = generateName('vm');
-    var vm = zone.vm(VM_NAME);
+    let VM_NAME = generateName('vm');
+    let vm = zone.vm(VM_NAME);
 
     before(create(vm, {os: 'ubuntu', http: true}));
 
@@ -1288,7 +1288,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of vms in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getVMsStream()
@@ -1307,12 +1307,12 @@ describe('Compute', function() {
     });
 
     it('should attach and detach a disk', function(done) {
-      var disk = zone.disk(generateName('disk'));
+      let disk = zone.disk(generateName('disk'));
 
       async.series([createDisk, attachDisk, detachDisk], done);
 
       function createDisk(callback) {
-        var config = {
+        let config = {
           os: 'ubuntu',
         };
 
@@ -1333,7 +1333,7 @@ describe('Compute', function() {
     });
 
     it('should set tags', function(done) {
-      var newTagName = 'new-tag';
+      let newTagName = 'new-tag';
 
       vm.getTags(function(err, tags, fingerprint) {
         assert.ifError(err);
@@ -1361,7 +1361,7 @@ describe('Compute', function() {
     });
 
     it('should resize the machine', function(done) {
-      var machineType = 'n1-standard-2';
+      let machineType = 'n1-standard-2';
 
       vm.resize(machineType, function(err) {
         assert.ifError(err);
@@ -1369,7 +1369,7 @@ describe('Compute', function() {
         vm.getMetadata(function(err, metadata) {
           assert.ifError(err);
 
-          var expectedMachineType = [
+          let expectedMachineType = [
             'https://www.googleapis.com/compute/v1',
             'zones',
             zone.id,
@@ -1391,10 +1391,10 @@ describe('Compute', function() {
     });
 
     it('should set metadata', function(done) {
-      var key = 'newKey';
-      var value = 'newValue';
+      let key = 'newKey';
+      let value = 'newValue';
 
-      var newMetadata = {};
+      let newMetadata = {};
       newMetadata[key] = value;
 
       vm.setMetadata(
@@ -1448,7 +1448,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of zones in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       compute
         .getZonesStream()
@@ -1471,7 +1471,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of disks in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       zone
         .getDisksStream()
@@ -1494,7 +1494,7 @@ describe('Compute', function() {
     });
 
     it('should get a list of operations in stream mode', function(done) {
-      var resultsMatched = 0;
+      let resultsMatched = 0;
 
       zone
         .getOperationsStream()
@@ -1649,11 +1649,11 @@ describe('Compute', function() {
   }
 
   function createService(name, instanceGroupName, healthCheckName, callback) {
-    var service = compute.service(name);
-    var group = zone.instanceGroup(instanceGroupName);
-    var healthCheck = compute.healthCheck(healthCheckName);
-    var groupUrl;
-    var healthCheckUrl;
+    let service = compute.service(name);
+    let group = zone.instanceGroup(instanceGroupName);
+    let healthCheck = compute.healthCheck(healthCheckName);
+    let groupUrl;
+    let healthCheckUrl;
 
     async.series(
       [
@@ -1764,7 +1764,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = compute.operation(resp.name);
+        let operation = compute.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
@@ -1784,7 +1784,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = compute.operation(resp.name);
+        let operation = compute.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
@@ -1833,7 +1833,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = compute.operation(resp.name);
+        let operation = compute.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
@@ -1853,7 +1853,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = compute.operation(resp.name);
+        let operation = compute.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
@@ -1905,7 +1905,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = zone.operation(resp.name);
+        let operation = zone.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
@@ -1925,7 +1925,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = zone.operation(resp.name);
+        let operation = zone.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
@@ -1957,7 +1957,7 @@ describe('Compute', function() {
         return;
       }
 
-      var names = resp.items.map(prop('name'));
+      let names = resp.items.map(prop('name'));
       async.each(names, deleteInstanceTemplate, callback);
     });
   }
@@ -2005,7 +2005,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = compute.operation(resp.name);
+        let operation = compute.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
@@ -2025,7 +2025,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = compute.operation(resp.name);
+        let operation = compute.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
@@ -2057,7 +2057,7 @@ describe('Compute', function() {
         return;
       }
 
-      var names = resp.items.map(prop('name'));
+      let names = resp.items.map(prop('name'));
       async.each(names, deleteInstanceGroupManager, callback);
     });
   }
@@ -2080,7 +2080,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = zone.operation(resp.name);
+        let operation = zone.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
@@ -2100,7 +2100,7 @@ describe('Compute', function() {
           return;
         }
 
-        var operation = zone.operation(resp.name);
+        let operation = zone.operation(resp.name);
         operation.on('error', callback).on('complete', function() {
           callback();
         });
diff --git a/test/address.js b/test/address.js
index 0dfe6f1c..f0c6f8b7 100644
--- a/test/address.js
+++ b/test/address.js
@@ -16,15 +16,15 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let assert = require('assert');
+let extend = require('extend');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Address') {
       promisified = true;
@@ -40,11 +40,11 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Address', function() {
-  var Address;
-  var address;
+  let Address;
+  let address;
 
-  var ADDRESS_NAME = 'us-central1';
-  var REGION = {
+  let ADDRESS_NAME = 'us-central1';
+  let REGION = {
     createAddress: util.noop,
   };
 
@@ -84,10 +84,10 @@ describe('Address', function() {
         },
       });
 
-      var address = new Address(regionInstance, ADDRESS_NAME);
+      let address = new Address(regionInstance, ADDRESS_NAME);
       assert(address instanceof ServiceObject);
 
-      var calledWith = address.calledWith_[0];
+      let calledWith = address.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, regionInstance);
       assert.strictEqual(calledWith.baseUrl, '/addresses');
@@ -113,8 +113,8 @@ describe('Address', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         address.request = function(reqOpts, callback) {
@@ -139,7 +139,7 @@ describe('Address', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -150,7 +150,7 @@ describe('Address', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         address.region.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/autoscaler.js b/test/autoscaler.js
index 8d680106..3c7aee58 100644
--- a/test/autoscaler.js
+++ b/test/autoscaler.js
@@ -16,15 +16,15 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let assert = require('assert');
+let extend = require('extend');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Autoscaler') {
       promisified = true;
@@ -40,13 +40,13 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Autoscaler', function() {
-  var Autoscaler;
-  var autoscaler;
+  let Autoscaler;
+  let autoscaler;
 
-  var AUTOSCALER_NAME = 'autoscaler-name';
+  let AUTOSCALER_NAME = 'autoscaler-name';
 
-  var COMPUTE = {projectId: 'project-id'};
-  var ZONE = {
+  let COMPUTE = {projectId: 'project-id'};
+  let ZONE = {
     compute: COMPUTE,
     name: 'us-central1-a',
     createAutoscaler: util.noop,
@@ -79,7 +79,7 @@ describe('Autoscaler', function() {
     });
 
     it('should inherit from ServiceObject', function() {
-      var createMethod = util.noop;
+      let createMethod = util.noop;
 
       var zoneInstance = extend({}, ZONE, {
         createAutoscaler: {
@@ -90,10 +90,10 @@ describe('Autoscaler', function() {
         },
       });
 
-      var autoscaler = new Autoscaler(zoneInstance, AUTOSCALER_NAME);
+      let autoscaler = new Autoscaler(zoneInstance, AUTOSCALER_NAME);
       assert(autoscaler instanceof ServiceObject);
 
-      var calledWith = autoscaler.calledWith_[0];
+      let calledWith = autoscaler.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, zoneInstance);
       assert.strictEqual(calledWith.baseUrl, '/autoscalers');
@@ -119,8 +119,8 @@ describe('Autoscaler', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -145,7 +145,7 @@ describe('Autoscaler', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -156,7 +156,7 @@ describe('Autoscaler', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         autoscaler.zone.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -182,7 +182,7 @@ describe('Autoscaler', function() {
 
   describe('setMetadata', function() {
     it('should make the correct API request', function(done) {
-      var metadata = {};
+      let metadata = {};
 
       autoscaler.zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.method, 'PATCH');
@@ -200,8 +200,8 @@ describe('Autoscaler', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         autoscaler.zone.request = function(reqOpts, callback) {
@@ -220,7 +220,7 @@ describe('Autoscaler', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -231,8 +231,8 @@ describe('Autoscaler', function() {
       });
 
       it('should execute callback with operation & response', function(done) {
-        var operation = {};
-        var metadata = {a: 'b'};
+        let operation = {};
+        let metadata = {a: 'b'};
 
         autoscaler.zone.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/disk.js b/test/disk.js
index 450b20b1..aa33a346 100644
--- a/test/disk.js
+++ b/test/disk.js
@@ -16,16 +16,16 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var format = require('string-format-obj');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let assert = require('assert');
+let extend = require('extend');
+let format = require('string-format-obj');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class, options) {
     if (Class.name !== 'Disk') {
       return;
@@ -48,21 +48,21 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Disk', function() {
-  var Disk;
-  var disk;
+  let Disk;
+  let disk;
 
-  var COMPUTE = {
+  let COMPUTE = {
     projectId: 'project-id',
   };
 
-  var ZONE = {
+  let ZONE = {
     compute: COMPUTE,
     name: 'us-central1-a',
     createDisk: util.noop,
   };
 
-  var DISK_NAME = 'disk-name';
-  var DISK_FULL_NAME = format('projects/{pId}/zones/{zName}/disks/{dName}', {
+  let DISK_NAME = 'disk-name';
+  let DISK_FULL_NAME = format('projects/{pId}/zones/{zName}/disks/{dName}', {
     pId: COMPUTE.projectId,
     zName: ZONE.name,
     dName: DISK_NAME,
@@ -96,8 +96,8 @@ describe('Disk', function() {
     });
 
     it('should format the disk name', function() {
-      var formatName_ = Disk.formatName_;
-      var formattedName = 'projects/a/zones/b/disks/c';
+      let formatName_ = Disk.formatName_;
+      let formattedName = 'projects/a/zones/b/disks/c';
 
       Disk.formatName_ = function(zone, name) {
         Disk.formatName_ = formatName_;
@@ -108,7 +108,7 @@ describe('Disk', function() {
         return formattedName;
       };
 
-      var disk = new Disk(ZONE, DISK_NAME);
+      let disk = new Disk(ZONE, DISK_NAME);
       assert(disk.formattedName, formattedName);
     });
 
@@ -122,10 +122,10 @@ describe('Disk', function() {
         },
       });
 
-      var disk = new Disk(zoneInstance, DISK_NAME);
+      let disk = new Disk(zoneInstance, DISK_NAME);
       assert(disk instanceof ServiceObject);
 
-      var calledWith = disk.calledWith_[0];
+      let calledWith = disk.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, zoneInstance);
       assert.strictEqual(calledWith.baseUrl, '/disks');
@@ -141,7 +141,7 @@ describe('Disk', function() {
 
   describe('formatName_', function() {
     it('should format the name', function() {
-      var formattedName_ = Disk.formatName_(ZONE, DISK_NAME);
+      let formattedName_ = Disk.formatName_(ZONE, DISK_NAME);
       assert.strictEqual(formattedName_, DISK_FULL_NAME);
     });
   });
@@ -159,8 +159,8 @@ describe('Disk', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         disk.request = function(reqOpts, callback) {
@@ -186,7 +186,7 @@ describe('Disk', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -197,8 +197,8 @@ describe('Disk', function() {
       });
 
       it('should execute callback with Snapshot & Operation', function(done) {
-        var snapshot = {};
-        var operation = {};
+        let snapshot = {};
+        let operation = {};
 
         disk.snapshot = function(name) {
           assert.strictEqual(name, 'test');
@@ -241,8 +241,8 @@ describe('Disk', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -267,7 +267,7 @@ describe('Disk', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -278,7 +278,7 @@ describe('Disk', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         disk.zone.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -303,10 +303,10 @@ describe('Disk', function() {
   });
 
   describe('snapshot', function() {
-    var NAME = 'snapshot-name';
+    let NAME = 'snapshot-name';
 
     it('should return a Snapshot object', function() {
-      var snapshot = disk.snapshot(NAME);
+      let snapshot = disk.snapshot(NAME);
       assert(snapshot instanceof FakeSnapshot);
       assert.strictEqual(snapshot.calledWith_[0], disk);
       assert.strictEqual(snapshot.calledWith_[1], NAME);
diff --git a/test/firewall.js b/test/firewall.js
index e97b6aa4..49c989ed 100644
--- a/test/firewall.js
+++ b/test/firewall.js
@@ -16,15 +16,15 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let assert = require('assert');
+let extend = require('extend');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Firewall') {
       promisified = true;
@@ -40,15 +40,15 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Firewall', function() {
-  var Firewall;
-  var firewall;
+  let Firewall;
+  let firewall;
 
-  var COMPUTE = {
+  let COMPUTE = {
     projectId: 'project-id',
     createFirewall: util.noop,
   };
-  var FIREWALL_NAME = 'tcp-3000';
-  var FIREWALL_NETWORK = 'global/networks/default';
+  let FIREWALL_NAME = 'tcp-3000';
+  let FIREWALL_NETWORK = 'global/networks/default';
 
   before(function() {
     Firewall = proxyquire('../src/firewall.js', {
@@ -89,11 +89,11 @@ describe('Firewall', function() {
         },
       });
 
-      var firewall = new Firewall(computeInstance, FIREWALL_NAME);
+      let firewall = new Firewall(computeInstance, FIREWALL_NAME);
 
       assert(firewall instanceof ServiceObject);
 
-      var calledWith = firewall.calledWith_[0];
+      let calledWith = firewall.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, computeInstance);
       assert.strictEqual(calledWith.baseUrl, '/global/firewalls');
@@ -118,8 +118,8 @@ describe('Firewall', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -144,7 +144,7 @@ describe('Firewall', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -155,7 +155,7 @@ describe('Firewall', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         firewall.compute.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -181,7 +181,7 @@ describe('Firewall', function() {
 
   describe('setMetadata', function() {
     it('should make the correct API request', function(done) {
-      var metadata = {};
+      let metadata = {};
 
       firewall.request = function(reqOpts) {
         assert.strictEqual(reqOpts.method, 'PATCH');
@@ -199,8 +199,8 @@ describe('Firewall', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         firewall.request = function(reqOpts, callback) {
@@ -219,7 +219,7 @@ describe('Firewall', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -230,8 +230,8 @@ describe('Firewall', function() {
       });
 
       it('should execute callback with operation & response', function(done) {
-        var operation = {};
-        var metadata = {a: 'b'};
+        let operation = {};
+        let metadata = {a: 'b'};
 
         firewall.compute.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/health-check.js b/test/health-check.js
index ecd774a8..066b2290 100644
--- a/test/health-check.js
+++ b/test/health-check.js
@@ -16,15 +16,15 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let assert = require('assert');
+let extend = require('extend');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'HealthCheck') {
       promisified = true;
@@ -39,14 +39,14 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('HealthCheck', function() {
-  var HealthCheck;
-  var healthCheck;
+  let HealthCheck;
+  let healthCheck;
 
-  var COMPUTE = {
+  let COMPUTE = {
     createHealthCheck: util.noop,
   };
-  var HEALTH_CHECK_NAME = 'health-check-name';
-  var OPTIONS = {};
+  let HEALTH_CHECK_NAME = 'health-check-name';
+  let OPTIONS = {};
 
   before(function() {
     HealthCheck = proxyquire('../src/health-check.js', {
@@ -69,7 +69,7 @@ describe('HealthCheck', function() {
     it('should inherit from ServiceObject', function() {
       assert(healthCheck instanceof FakeServiceObject);
 
-      var calledWith = healthCheck.calledWith_[0];
+      let calledWith = healthCheck.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, COMPUTE);
       assert.strictEqual(calledWith.id, HEALTH_CHECK_NAME);
@@ -87,17 +87,17 @@ describe('HealthCheck', function() {
 
     describe('http', function() {
       it('should set the correct baseUrl', function() {
-        var calledWith = healthCheck.calledWith_[0];
+        let calledWith = healthCheck.calledWith_[0];
 
         assert.strictEqual(calledWith.baseUrl, '/global/httpHealthChecks');
       });
 
       it('should not set options.https when created', function(done) {
-        var createMethod = healthCheck.calledWith_[0].createMethod;
+        let createMethod = healthCheck.calledWith_[0].createMethod;
 
-        var NAME = 'name';
-        var OPTIONS = {a: 'b'};
-        var originalOptions = extend({}, OPTIONS);
+        let NAME = 'name';
+        let OPTIONS = {a: 'b'};
+        let originalOptions = extend({}, OPTIONS);
 
         COMPUTE.createHealthCheck = function(name, opts, callback) {
           assert.strictEqual(name, NAME);
@@ -110,7 +110,7 @@ describe('HealthCheck', function() {
       });
 
       it('should not require a callback when creating', function(done) {
-        var createMethod = healthCheck.calledWith_[0].createMethod;
+        let createMethod = healthCheck.calledWith_[0].createMethod;
 
         COMPUTE.createHealthCheck = function(name, opts, callback) {
           assert.deepStrictEqual(opts, {});
@@ -122,7 +122,7 @@ describe('HealthCheck', function() {
     });
 
     describe('https', function() {
-      var healthCheck;
+      let healthCheck;
 
       beforeEach(function() {
         healthCheck = new HealthCheck(COMPUTE, HEALTH_CHECK_NAME, {
@@ -131,17 +131,17 @@ describe('HealthCheck', function() {
       });
 
       it('should set the correct baseUrl', function() {
-        var calledWith = healthCheck.calledWith_[0];
+        let calledWith = healthCheck.calledWith_[0];
 
         assert.strictEqual(calledWith.baseUrl, '/global/httpsHealthChecks');
       });
 
       it('should set options.https = true when created', function(done) {
-        var createMethod = healthCheck.calledWith_[0].createMethod;
+        let createMethod = healthCheck.calledWith_[0].createMethod;
 
-        var NAME = 'name';
-        var OPTIONS = {a: 'b'};
-        var originalOptions = extend({}, OPTIONS);
+        let NAME = 'name';
+        let OPTIONS = {a: 'b'};
+        let originalOptions = extend({}, OPTIONS);
 
         COMPUTE.createHealthCheck = function(name, opts, callback) {
           assert.strictEqual(name, NAME);
@@ -154,7 +154,7 @@ describe('HealthCheck', function() {
       });
 
       it('should not require a callback when creating', function(done) {
-        var createMethod = healthCheck.calledWith_[0].createMethod;
+        let createMethod = healthCheck.calledWith_[0].createMethod;
 
         COMPUTE.createHealthCheck = function(name, opts, callback) {
           assert.deepStrictEqual(opts, {https: true});
@@ -177,8 +177,8 @@ describe('HealthCheck', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -203,7 +203,7 @@ describe('HealthCheck', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -214,7 +214,7 @@ describe('HealthCheck', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         healthCheck.compute.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -239,7 +239,7 @@ describe('HealthCheck', function() {
   });
 
   describe('setMetadata', function() {
-    var METADATA = {};
+    let METADATA = {};
 
     it('should call ServiceObject.setMetadata', function(done) {
       FakeServiceObject.prototype.setMetadata = function(metadata) {
@@ -252,8 +252,8 @@ describe('HealthCheck', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {};
+      let error = new Error('Error.');
+      let apiResponse = {};
 
       beforeEach(function() {
         FakeServiceObject.prototype.setMetadata = function(metadata, callback) {
@@ -272,7 +272,7 @@ describe('HealthCheck', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -283,8 +283,8 @@ describe('HealthCheck', function() {
       });
 
       it('should execute callback with operation & response', function(done) {
-        var operation = {};
-        var metadata = {a: 'b'};
+        let operation = {};
+        let metadata = {a: 'b'};
 
         healthCheck.compute.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/image.js b/test/image.js
index 2c494939..3e22aa75 100644
--- a/test/image.js
+++ b/test/image.js
@@ -16,15 +16,15 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let assert = require('assert');
+let extend = require('extend');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Image') {
       promisified = true;
@@ -40,15 +40,15 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Image', function() {
-  var Image;
-  var image;
+  let Image;
+  let image;
 
-  var COMPUTE = {
+  let COMPUTE = {
     projectId: 'project-id',
     createImage: util.noop,
     operation: util.noop,
   };
-  var IMAGE_NAME = 'image-name';
+  let IMAGE_NAME = 'image-name';
 
   before(function() {
     Image = proxyquire('../src/image.js', {
@@ -78,10 +78,10 @@ describe('Image', function() {
         },
       });
 
-      var image = new Image(computeInstance, IMAGE_NAME);
+      let image = new Image(computeInstance, IMAGE_NAME);
       assert(image instanceof ServiceObject);
 
-      var calledWith = image.calledWith_[0];
+      let calledWith = image.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, computeInstance);
       assert.strictEqual(calledWith.baseUrl, '/global/images');
@@ -106,8 +106,8 @@ describe('Image', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -132,7 +132,7 @@ describe('Image', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -143,7 +143,7 @@ describe('Image', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         image.parent.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/index.js b/test/index.js
index 55ef2143..599a50b1 100644
--- a/test/index.js
+++ b/test/index.js
@@ -16,20 +16,20 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var assert = require('assert');
-var events = require('events');
-var extend = require('extend');
-var format = require('string-format-obj');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var Service = require('@google-cloud/common').Service;
-var util = require('@google-cloud/common').util;
-
-var slice = Array.prototype.slice;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let arrify = require('arrify');
+let assert = require('assert');
+let events = require('events');
+let extend = require('extend');
+let format = require('string-format-obj');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let Service = require('@google-cloud/common').Service;
+let util = require('@google-cloud/common').util;
+
+let slice = Array.prototype.slice;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   makeAuthenticatedRequestFactory: util.noop,
   promisifyAll: function(Class, options) {
     if (Class.name !== 'Compute') {
@@ -59,9 +59,9 @@ var fakeUtil = extend({}, util, {
     ]);
   },
 });
-var originalFakeUtil = extend(true, {}, fakeUtil);
+let originalFakeUtil = extend(true, {}, fakeUtil);
 
-var fakePaginator = {
+let fakePaginator = {
   extend: function(Class, methods) {
     if (Class.name !== 'Compute') {
       return;
@@ -160,10 +160,10 @@ function FakeService() {
 nodeutil.inherits(FakeService, Service);
 
 describe('Compute', function() {
-  var Compute;
-  var compute;
+  let Compute;
+  let compute;
 
-  var PROJECT_ID = 'project-id';
+  let PROJECT_ID = 'project-id';
 
   before(function() {
     // Node v4 on Circle times out.
@@ -198,13 +198,13 @@ describe('Compute', function() {
 
   describe('instantiation', function() {
     it('should return a new instance of Compute', function() {
-      var compute = new Compute({projectId: PROJECT_ID});
+      let compute = new Compute({projectId: PROJECT_ID});
       assert(compute instanceof Compute);
     });
 
     it('should normalize the arguments', function() {
-      var normalizeArgumentsCalled = false;
-      var options = {};
+      let normalizeArgumentsCalled = false;
+      let options = {};
 
       fakeUtil.normalizeArguments = function(context, options_) {
         normalizeArgumentsCalled = true;
@@ -219,9 +219,9 @@ describe('Compute', function() {
     it('should inherit from Service', function() {
       assert(compute instanceof Service);
 
-      var calledWith = compute.calledWith_[0];
+      let calledWith = compute.calledWith_[0];
 
-      var baseUrl = 'https://www.googleapis.com/compute/v1';
+      let baseUrl = 'https://www.googleapis.com/compute/v1';
       assert.strictEqual(calledWith.baseUrl, baseUrl);
       assert.deepStrictEqual(calledWith.scopes, [
         'https://www.googleapis.com/auth/compute',
@@ -272,7 +272,7 @@ describe('Compute', function() {
 
     describe('config.protocols', function() {
       it('should format protocols', function(done) {
-        var options = {
+        let options = {
           allowed: {
             IPProtocol: 'http',
             ports: [8000],
@@ -303,7 +303,7 @@ describe('Compute', function() {
 
     describe('config.ranges', function() {
       it('should format ranges to sourceRanges', function(done) {
-        var options = {
+        let options = {
           ranges: '0.0.0.0/0', // non-array to test that it's arrified.
         };
 
@@ -319,7 +319,7 @@ describe('Compute', function() {
 
     describe('config.tags', function() {
       it('should format tags to sourceTags', function(done) {
-        var options = {
+        let options = {
           tags: 'tag', // non-array to test that it's arrified.
         };
 
@@ -334,7 +334,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var name = 'new-firewall-name';
+      let name = 'new-firewall-name';
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.method, 'POST');
@@ -347,8 +347,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -368,7 +368,7 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -379,9 +379,9 @@ describe('Compute', function() {
       });
 
       it('should exec cb with Firewall, Operation & apiResp', function(done) {
-        var name = 'name';
-        var firewall = {};
-        var operation = {};
+        let name = 'name';
+        let firewall = {};
+        let operation = {};
 
         compute.firewall = function(name_) {
           assert.strictEqual(name_, name);
@@ -414,7 +414,7 @@ describe('Compute', function() {
 
     describe('options.interval', function() {
       it('should set checkIntervalSec', function(done) {
-        var options = {interval: 50};
+        let options = {interval: 50};
 
         compute.request = function(reqOpts) {
           assert.strictEqual(reqOpts.json.checkIntervalSec, options.interval);
@@ -428,7 +428,7 @@ describe('Compute', function() {
 
     describe('config.timeout', function() {
       it('should set timeoutSec', function(done) {
-        var options = {timeout: 50};
+        let options = {timeout: 50};
 
         compute.request = function(reqOpts) {
           assert.strictEqual(reqOpts.json.timeoutSec, options.timeout);
@@ -442,7 +442,7 @@ describe('Compute', function() {
 
     describe('options.https', function() {
       it('should make the correct API request', function(done) {
-        var name = 'https-health-check-name';
+        let name = 'https-health-check-name';
 
         compute.request = function(reqOpts) {
           assert.strictEqual(reqOpts.json.https, undefined);
@@ -456,9 +456,9 @@ describe('Compute', function() {
     });
 
     it('should make the correct default API request', function(done) {
-      var name = 'new-health-check-name';
-      var options = {a: 'b'};
-      var originalOptions = extend({}, options);
+      let name = 'new-health-check-name';
+      let options = {a: 'b'};
+      let originalOptions = extend({}, options);
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.method, 'POST');
@@ -472,8 +472,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -493,7 +493,7 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -504,9 +504,9 @@ describe('Compute', function() {
       });
 
       it('should exec cb with HealthCheck, Op, & apiResp', function(done) {
-        var name = 'name';
-        var healthCheck = {};
-        var operation = {};
+        let name = 'name';
+        let healthCheck = {};
+        let operation = {};
 
         compute.healthCheck = function(name_, options) {
           assert.strictEqual(name_, name);
@@ -530,7 +530,7 @@ describe('Compute', function() {
       });
 
       it('should create an HTTPS HealthCheck object', function(done) {
-        var name = 'name';
+        let name = 'name';
 
         compute.healthCheck = function(name_, options) {
           assert.strictEqual(name_, name);
@@ -544,9 +544,9 @@ describe('Compute', function() {
   });
 
   describe('createImage', function() {
-    var NAME = 'image-name';
+    let NAME = 'image-name';
 
-    var DISK = {
+    let DISK = {
       name: 'disk-name',
       zone: {
         name: 'zone-name',
@@ -572,7 +572,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {
+      let options = {
         a: 'b',
         c: 'd',
       };
@@ -597,8 +597,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {};
+      let error = new Error('Error.');
+      let apiResponse = {};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -617,7 +617,7 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -628,8 +628,8 @@ describe('Compute', function() {
       });
 
       it('should exec cb with Operation & apiResp', function(done) {
-        var network = {};
-        var operation = {};
+        let network = {};
+        let operation = {};
 
         compute.network = function(name) {
           assert.strictEqual(name, NAME);
@@ -655,7 +655,7 @@ describe('Compute', function() {
   describe('createNetwork', function() {
     describe('config.range', function() {
       it('should set the IPv4Range', function(done) {
-        var options = {
+        let options = {
           range: '10.240.0.0/16',
         };
 
@@ -671,7 +671,7 @@ describe('Compute', function() {
 
     describe('config.gateway', function() {
       it('should set the gatewayIPv4', function(done) {
-        var options = {
+        let options = {
           gateway: '10.1.1.1',
         };
 
@@ -686,7 +686,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var name = 'new-network';
+      let name = 'new-network';
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.method, 'POST');
@@ -699,8 +699,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -720,8 +720,8 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var NAME = 'network-name';
-      var apiResponse = {
+      let NAME = 'network-name';
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -732,8 +732,8 @@ describe('Compute', function() {
       });
 
       it('should exec cb with Network, Operation & apiResp', function(done) {
-        var network = {};
-        var operation = {};
+        let network = {};
+        let operation = {};
 
         compute.network = function(name_) {
           assert.strictEqual(name_, NAME);
@@ -758,12 +758,12 @@ describe('Compute', function() {
   });
 
   describe('createRule', function() {
-    var NAME = 'new-rule';
+    let NAME = 'new-rule';
 
     it('should make the correct API request', function(done) {
-      var config = {a: 'b'};
-      var originalConfig = extend({}, config);
-      var expectedConfig = extend({}, config, {name: NAME});
+      let config = {a: 'b'};
+      let originalConfig = extend({}, config);
+      let expectedConfig = extend({}, config, {name: NAME});
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.method, 'POST');
@@ -777,7 +777,7 @@ describe('Compute', function() {
     });
 
     describe('config.ip', function() {
-      var CONFIG = {
+      let CONFIG = {
         ip: '0.0.0.0',
       };
 
@@ -795,7 +795,7 @@ describe('Compute', function() {
     });
 
     describe('config.protocol', function() {
-      var CONFIG = {
+      let CONFIG = {
         protocol: 'TCP',
       };
 
@@ -813,7 +813,7 @@ describe('Compute', function() {
     });
 
     describe('config.range', function() {
-      var CONFIG = {
+      let CONFIG = {
         range: '200-300',
       };
 
@@ -831,8 +831,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -852,7 +852,7 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -863,8 +863,8 @@ describe('Compute', function() {
       });
 
       it('should exec cb with Rule, Operation & apiResp', function(done) {
-        var rule = {};
-        var operation = {};
+        let rule = {};
+        let operation = {};
 
         compute.rule = function(name) {
           assert.strictEqual(name, NAME);
@@ -889,7 +889,7 @@ describe('Compute', function() {
   });
 
   describe('createService', function() {
-    var NAME = 'new-service';
+    let NAME = 'new-service';
 
     it('should make the correct API request', function(done) {
       compute.request = function(reqOpts) {
@@ -903,8 +903,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -924,7 +924,7 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -935,8 +935,8 @@ describe('Compute', function() {
       });
 
       it('should exec cb with Service, Operation & apiResp', function(done) {
-        var service = {};
-        var operation = {};
+        let service = {};
+        let operation = {};
 
         compute.service = function(name) {
           assert.strictEqual(name, NAME);
@@ -961,10 +961,10 @@ describe('Compute', function() {
   });
 
   describe('firewall', function() {
-    var NAME = 'firewall-name';
+    let NAME = 'firewall-name';
 
     it('should return a Firewall object', function() {
-      var firewall = compute.firewall(NAME);
+      let firewall = compute.firewall(NAME);
       assert(firewall instanceof FakeFirewall);
       assert.strictEqual(firewall.calledWith_[0], compute);
       assert.strictEqual(firewall.calledWith_[1], NAME);
@@ -982,7 +982,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/aggregated/addresses');
@@ -994,8 +994,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1016,11 +1016,11 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var REGION_NAME = 'region-1';
-      var FULL_REGION_NAME = 'regions/' + REGION_NAME;
+      let REGION_NAME = 'region-1';
+      let FULL_REGION_NAME = 'regions/' + REGION_NAME;
 
-      var address = {name: 'address-1'};
-      var apiResponse = {
+      let address = {name: 'address-1'};
+      let apiResponse = {
         items: {},
       };
 
@@ -1035,7 +1035,7 @@ describe('Compute', function() {
       });
 
       it('should create Address objects from the response', function(done) {
-        var region = {};
+        let region = {};
 
         compute.region = function(name) {
           assert.strictEqual(name, REGION_NAME);
@@ -1052,12 +1052,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -1092,7 +1092,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/aggregated/autoscalers');
@@ -1104,8 +1104,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1126,11 +1126,11 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var ZONE_NAME = 'us-central1-a';
-      var FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
+      let ZONE_NAME = 'us-central1-a';
+      let FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
 
-      var autoscaler = {name: 'autoscaler-1'};
-      var apiResponse = {
+      let autoscaler = {name: 'autoscaler-1'};
+      let apiResponse = {
         items: {},
       };
 
@@ -1149,7 +1149,7 @@ describe('Compute', function() {
       });
 
       it('should create Autoscaler objects from the response', function(done) {
-        var zone = {};
+        let zone = {};
 
         compute.zone = function(name) {
           assert.strictEqual(name, ZONE_NAME);
@@ -1166,7 +1166,7 @@ describe('Compute', function() {
       });
 
       it('should not create zone-less Autoscalers', function(done) {
-        var zone = {};
+        let zone = {};
 
         compute.zone = function() {
           return zone;
@@ -1185,14 +1185,14 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
         delete apiResponseWithNextPageToken.items;
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -1227,7 +1227,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/aggregated/disks');
@@ -1239,8 +1239,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1261,11 +1261,11 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var ZONE_NAME = 'zone-1';
-      var FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
+      let ZONE_NAME = 'zone-1';
+      let FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
 
-      var disk = {name: 'disk-1'};
-      var apiResponse = {
+      let disk = {name: 'disk-1'};
+      let apiResponse = {
         items: {},
       };
 
@@ -1280,7 +1280,7 @@ describe('Compute', function() {
       });
 
       it('should create Disk objects from the response', function(done) {
-        var zone = {};
+        let zone = {};
 
         compute.zone = function(name) {
           assert.strictEqual(name, ZONE_NAME);
@@ -1297,12 +1297,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -1337,7 +1337,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/global/firewalls');
@@ -1349,8 +1349,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1371,8 +1371,8 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var firewall = {name: 'firewall-1'};
-      var apiResponse = {
+      let firewall = {name: 'firewall-1'};
+      let apiResponse = {
         items: [firewall],
       };
 
@@ -1393,12 +1393,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -1433,7 +1433,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct default API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/global/httpHealthChecks');
@@ -1446,8 +1446,8 @@ describe('Compute', function() {
 
     describe('options.https', function() {
       it('should make the correct API request', function(done) {
-        var options = {https: true};
-        var originalOptions = extend({}, options);
+        let options = {https: true};
+        let originalOptions = extend({}, options);
 
         compute.request = function(reqOpts) {
           assert.strictEqual(reqOpts.uri, '/global/httpsHealthChecks');
@@ -1461,8 +1461,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1483,8 +1483,8 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var healthCheck = {name: 'health-check-1'};
-      var apiResponse = {items: [healthCheck]};
+      let healthCheck = {name: 'health-check-1'};
+      let apiResponse = {items: [healthCheck]};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1515,12 +1515,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -1555,7 +1555,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/global/images');
@@ -1567,8 +1567,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1589,8 +1589,8 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var image = {name: 'image-1'};
-      var apiResponse = {
+      let image = {name: 'image-1'};
+      let apiResponse = {
         items: [image],
       };
 
@@ -1611,12 +1611,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -1651,7 +1651,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct default API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/aggregated/instanceGroups');
@@ -1663,8 +1663,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1685,11 +1685,11 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var ZONE_NAME = 'zone-1';
-      var FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
+      let ZONE_NAME = 'zone-1';
+      let FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
 
-      var instanceGroup = {name: 'instance-group-1'};
-      var apiResponse = {
+      let instanceGroup = {name: 'instance-group-1'};
+      let apiResponse = {
         items: {},
       };
 
@@ -1704,7 +1704,7 @@ describe('Compute', function() {
       });
 
       it('should create InstanceGroup objects from the resp', function(done) {
-        var zone = {};
+        let zone = {};
 
         compute.zone = function(name) {
           assert.strictEqual(name, ZONE_NAME);
@@ -1721,14 +1721,14 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
         delete apiResponseWithNextPageToken.items;
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -1763,7 +1763,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/aggregated/machineTypes');
@@ -1775,8 +1775,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {};
+      let error = new Error('Error.');
+      let apiResponse = {};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1796,11 +1796,11 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var ZONE_NAME = 'zone-1';
-      var FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
+      let ZONE_NAME = 'zone-1';
+      let FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
 
-      var machineType = {name: 'machineType-1'};
-      var apiResponse = {
+      let machineType = {name: 'machineType-1'};
+      let apiResponse = {
         items: {},
       };
 
@@ -1815,8 +1815,8 @@ describe('Compute', function() {
       });
 
       it('should create MachineType objects from the response', function(done) {
-        var zone = {};
-        var machineTypeInstance = {};
+        let zone = {};
+        let machineTypeInstance = {};
 
         compute.zone = function(name) {
           assert.strictEqual(name, ZONE_NAME);
@@ -1839,12 +1839,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -1879,7 +1879,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/global/networks');
@@ -1891,8 +1891,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -1913,8 +1913,8 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var network = {name: 'network-1'};
-      var apiResponse = {
+      let network = {name: 'network-1'};
+      let apiResponse = {
         items: [network],
       };
 
@@ -1935,12 +1935,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -1975,7 +1975,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/global/operations');
@@ -1987,8 +1987,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -2009,8 +2009,8 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var operation = {name: 'op-1'};
-      var apiResponse = {
+      let operation = {name: 'op-1'};
+      let apiResponse = {
         items: [operation],
       };
 
@@ -2031,12 +2031,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -2071,7 +2071,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/regions');
@@ -2083,8 +2083,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -2105,8 +2105,8 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var region = {name: 'region-1'};
-      var apiResponse = {
+      let region = {name: 'region-1'};
+      let apiResponse = {
         items: [region],
       };
 
@@ -2127,12 +2127,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -2167,7 +2167,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/global/forwardingRules');
@@ -2179,8 +2179,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -2201,10 +2201,10 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var rule = {
+      let rule = {
         name: 'rule-1',
       };
-      var apiResponse = {
+      let apiResponse = {
         items: [rule],
       };
 
@@ -2228,15 +2228,15 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {
+        let query = {
           a: 'b',
           c: 'd',
         };
-        var originalQuery = extend({}, query);
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -2271,7 +2271,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/global/backendServices');
@@ -2283,8 +2283,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -2305,10 +2305,10 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var service = {
+      let service = {
         name: 'service-1',
       };
-      var apiResponse = {
+      let apiResponse = {
         items: [service],
       };
 
@@ -2329,15 +2329,15 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {
+        let query = {
           a: 'b',
           c: 'd',
         };
-        var originalQuery = extend({}, query);
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -2372,7 +2372,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/global/snapshots');
@@ -2384,8 +2384,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -2406,8 +2406,8 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var snapshot = {name: 'snapshot-1'};
-      var apiResponse = {
+      let snapshot = {name: 'snapshot-1'};
+      let apiResponse = {
         items: [snapshot],
       };
 
@@ -2428,12 +2428,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -2468,7 +2468,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/aggregated/subnetworks');
@@ -2480,8 +2480,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -2502,11 +2502,11 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var REGION_NAME = 'region-1';
-      var FULL_REGION_NAME = 'regions/' + REGION_NAME;
+      let REGION_NAME = 'region-1';
+      let FULL_REGION_NAME = 'regions/' + REGION_NAME;
 
-      var subnetwork = {name: 'subnetwork-1'};
-      var apiResponse = {
+      let subnetwork = {name: 'subnetwork-1'};
+      let apiResponse = {
         items: {},
       };
 
@@ -2521,8 +2521,8 @@ describe('Compute', function() {
       });
 
       it('should create Subnetwork objects from the response', function(done) {
-        var region = {};
-        var fakeSubnetwork = {};
+        let region = {};
+        let fakeSubnetwork = {};
 
         compute.region = function(name) {
           assert.strictEqual(name, REGION_NAME);
@@ -2548,12 +2548,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -2588,7 +2588,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/aggregated/instances');
@@ -2600,8 +2600,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -2622,11 +2622,11 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var ZONE_NAME = 'zone-1';
-      var FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
+      let ZONE_NAME = 'zone-1';
+      let FULL_ZONE_NAME = 'zones/' + ZONE_NAME;
 
-      var vm = {name: 'vm-1'};
-      var apiResponse = {
+      let vm = {name: 'vm-1'};
+      let apiResponse = {
         items: {},
       };
 
@@ -2641,7 +2641,7 @@ describe('Compute', function() {
       });
 
       it('should create VM objects from the response', function(done) {
-        var zone = {};
+        let zone = {};
 
         compute.zone = function(name) {
           assert.strictEqual(name, ZONE_NAME);
@@ -2658,12 +2658,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -2698,7 +2698,7 @@ describe('Compute', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var options = {};
+      let options = {};
 
       compute.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/zones');
@@ -2710,8 +2710,8 @@ describe('Compute', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         compute.request = function(reqOpts, callback) {
@@ -2732,8 +2732,8 @@ describe('Compute', function() {
     });
 
     describe('success', function() {
-      var zone = {name: 'zone-1'};
-      var apiResponse = {
+      let zone = {name: 'zone-1'};
+      let apiResponse = {
         items: [zone],
       };
 
@@ -2754,12 +2754,12 @@ describe('Compute', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: 'next-page-token',
         });
 
-        var query = {a: 'b', c: 'd'};
-        var originalQuery = extend({}, query);
+        let query = {a: 'b', c: 'd'};
+        let originalQuery = extend({}, query);
 
         compute.request = function(reqOpts, callback) {
           callback(null, apiResponseWithNextPageToken);
@@ -2784,11 +2784,11 @@ describe('Compute', function() {
   });
 
   describe('healthCheck', function() {
-    var NAME = 'health-check-name';
-    var OPTIONS = {};
+    let NAME = 'health-check-name';
+    let OPTIONS = {};
 
     it('should return a HealthCheck object', function() {
-      var healthCheck = compute.healthCheck(NAME, OPTIONS);
+      let healthCheck = compute.healthCheck(NAME, OPTIONS);
       assert(healthCheck instanceof FakeHealthCheck);
       assert.strictEqual(healthCheck.calledWith_[0], compute);
       assert.strictEqual(healthCheck.calledWith_[1], NAME);
@@ -2797,10 +2797,10 @@ describe('Compute', function() {
   });
 
   describe('image', function() {
-    var NAME = 'image-name';
+    let NAME = 'image-name';
 
     it('should return an Image object', function() {
-      var image = compute.image(NAME);
+      let image = compute.image(NAME);
       assert(image instanceof FakeImage);
       assert.strictEqual(image.calledWith_[0], compute);
       assert.strictEqual(image.calledWith_[1], NAME);
@@ -2808,10 +2808,10 @@ describe('Compute', function() {
   });
 
   describe('network', function() {
-    var NAME = 'network-name';
+    let NAME = 'network-name';
 
     it('should return a Network object', function() {
-      var network = compute.network(NAME);
+      let network = compute.network(NAME);
       assert(network instanceof FakeNetwork);
       assert.strictEqual(network.calledWith_[0], compute);
       assert.strictEqual(network.calledWith_[1], NAME);
@@ -2819,10 +2819,10 @@ describe('Compute', function() {
   });
 
   describe('operation', function() {
-    var NAME = 'op-name';
+    let NAME = 'op-name';
 
     it('should return an Operation object', function() {
-      var op = compute.operation(NAME);
+      let op = compute.operation(NAME);
       assert(op instanceof FakeOperation);
       assert.strictEqual(op.calledWith_[0], compute);
       assert.strictEqual(op.calledWith_[1], NAME);
@@ -2831,17 +2831,17 @@ describe('Compute', function() {
 
   describe('project', function() {
     it('should return a Project object', function() {
-      var project = compute.project();
+      let project = compute.project();
       assert(project instanceof FakeProject);
       assert.strictEqual(project.calledWith_[0], compute);
     });
   });
 
   describe('region', function() {
-    var NAME = 'region-name';
+    let NAME = 'region-name';
 
     it('should return a Region object', function() {
-      var region = compute.region(NAME);
+      let region = compute.region(NAME);
       assert(region instanceof FakeRegion);
       assert.strictEqual(region.calledWith_[0], compute);
       assert.strictEqual(region.calledWith_[1], NAME);
@@ -2849,10 +2849,10 @@ describe('Compute', function() {
   });
 
   describe('rule', function() {
-    var NAME = 'rule-name';
+    let NAME = 'rule-name';
 
     it('should return a Rule object', function() {
-      var rule = compute.rule(NAME);
+      let rule = compute.rule(NAME);
       assert(rule instanceof FakeRule);
       assert.strictEqual(rule.calledWith_[0], compute);
       assert.strictEqual(rule.calledWith_[1], NAME);
@@ -2860,10 +2860,10 @@ describe('Compute', function() {
   });
 
   describe('service', function() {
-    var NAME = 'service-name';
+    let NAME = 'service-name';
 
     it('should return a Service object', function() {
-      var service = compute.service(NAME);
+      let service = compute.service(NAME);
       assert(service instanceof FakeServiceClass);
       assert.strictEqual(service.calledWith_[0], compute);
       assert.strictEqual(service.calledWith_[1], NAME);
@@ -2871,10 +2871,10 @@ describe('Compute', function() {
   });
 
   describe('snapshot', function() {
-    var NAME = 'snapshot-name';
+    let NAME = 'snapshot-name';
 
     it('should return a Snapshot object', function() {
-      var snapshot = compute.snapshot(NAME);
+      let snapshot = compute.snapshot(NAME);
       assert(snapshot instanceof FakeSnapshot);
       assert.strictEqual(snapshot.calledWith_[0], compute);
       assert.strictEqual(snapshot.calledWith_[1], NAME);
@@ -2882,10 +2882,10 @@ describe('Compute', function() {
   });
 
   describe('zone', function() {
-    var NAME = 'zone-name';
+    let NAME = 'zone-name';
 
     it('should return a Zone object', function() {
-      var zone = compute.zone(NAME);
+      let zone = compute.zone(NAME);
       assert(zone instanceof FakeZone);
       assert.strictEqual(zone.calledWith_[0], compute);
       assert.strictEqual(zone.calledWith_[1], NAME);
@@ -2893,11 +2893,11 @@ describe('Compute', function() {
   });
 
   describe('execAfterOperation_', function() {
-    var OPERATION = new events.EventEmitter();
+    let OPERATION = new events.EventEmitter();
 
     it('should execute callback with error & API response', function(done) {
-      var error = new Error('Error.');
-      var apiResponse = {};
+      let error = new Error('Error.');
+      let apiResponse = {};
 
       function onComplete(err, apiResponse_) {
         assert.strictEqual(err, error);
@@ -2905,14 +2905,14 @@ describe('Compute', function() {
         done();
       }
 
-      var execWithOperation = compute.execAfterOperation_(onComplete);
+      let execWithOperation = compute.execAfterOperation_(onComplete);
 
       execWithOperation(error, OPERATION, apiResponse);
     });
 
     it('should support variable arity', function(done) {
-      var error = new Error('Error.');
-      var apiResponse = {};
+      let error = new Error('Error.');
+      let apiResponse = {};
 
       function onComplete(err, apiResponse_) {
         assert.strictEqual(err, error);
@@ -2920,13 +2920,13 @@ describe('Compute', function() {
         done();
       }
 
-      var execWithOperation = compute.execAfterOperation_(onComplete);
+      let execWithOperation = compute.execAfterOperation_(onComplete);
 
       execWithOperation(error, null, null, OPERATION, apiResponse);
     });
 
     it('should register callback on operation error', function(done) {
-      var apiResponse = {};
+      let apiResponse = {};
 
       function onComplete() {}
 
@@ -2936,12 +2936,12 @@ describe('Compute', function() {
         done();
       });
 
-      var execWithOperation = compute.execAfterOperation_(onComplete);
+      let execWithOperation = compute.execAfterOperation_(onComplete);
       execWithOperation(null, OPERATION, apiResponse);
     });
 
     it('should execute callback on operation complete', function(done) {
-      var apiResponse = {};
+      let apiResponse = {};
 
       function onComplete(err, apiResponse_) {
         assert.strictEqual(err, null);
@@ -2949,7 +2949,7 @@ describe('Compute', function() {
         done();
       }
 
-      var execWithOperation = compute.execAfterOperation_(onComplete);
+      let execWithOperation = compute.execAfterOperation_(onComplete);
       execWithOperation(null, OPERATION, {});
 
       OPERATION.emit('complete', apiResponse);
diff --git a/test/instance-group.js b/test/instance-group.js
index 7e043aa6..28957db2 100644
--- a/test/instance-group.js
+++ b/test/instance-group.js
@@ -16,17 +16,17 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
+let arrify = require('arrify');
+let assert = require('assert');
+let extend = require('extend');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
 
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
 
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'InstanceGroup') {
       promisified = true;
@@ -41,8 +41,8 @@ function FakeServiceObject() {
 
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
-var extended = false;
-var fakePaginator = {
+let extended = false;
+let fakePaginator = {
   extend: function(Class, methods) {
     if (Class.name !== 'InstanceGroup') {
       return;
@@ -59,16 +59,16 @@ var fakePaginator = {
 };
 
 describe('InstanceGroup', function() {
-  var InstanceGroup;
-  var instanceGroup;
+  let InstanceGroup;
+  let instanceGroup;
 
-  var staticMethods = {};
+  let staticMethods = {};
 
-  var ZONE = {
+  let ZONE = {
     createInstanceGroup: util.noop,
     vm: util.noop,
   };
-  var NAME = 'instance-group-name';
+  let NAME = 'instance-group-name';
 
   before(function() {
     InstanceGroup = proxyquire('../src/instance-group.js', {
@@ -108,7 +108,7 @@ describe('InstanceGroup', function() {
     });
 
     it('should inherit from ServiceObject', function(done) {
-      var instanceGroup;
+      let instanceGroup;
 
       var zoneInstance = extend({}, ZONE, {
         createInstanceGroup: {
@@ -118,7 +118,7 @@ describe('InstanceGroup', function() {
             setImmediate(function() {
               assert(instanceGroup instanceof ServiceObject);
 
-              var calledWith = instanceGroup.calledWith_[0];
+              let calledWith = instanceGroup.calledWith_[0];
 
               assert.strictEqual(calledWith.parent, zoneInstance);
               assert.strictEqual(calledWith.baseUrl, '/instanceGroups');
@@ -141,7 +141,7 @@ describe('InstanceGroup', function() {
   });
 
   describe('formatPorts_', function() {
-    var PORTS = {
+    let PORTS = {
       http: 80,
       https: 443,
     };
@@ -155,7 +155,7 @@ describe('InstanceGroup', function() {
   });
 
   describe('add', function() {
-    var VMS = [{url: 'vm-url'}, {url: 'vm-url-2'}];
+    let VMS = [{url: 'vm-url'}, {url: 'vm-url-2'}];
 
     it('should make the correct API request', function(done) {
       instanceGroup.request = function(reqOpts) {
@@ -176,8 +176,8 @@ describe('InstanceGroup', function() {
     });
 
     describe('error', function() {
-      var apiResponse = {};
-      var error = new Error('Error.');
+      let apiResponse = {};
+      let error = new Error('Error.');
 
       beforeEach(function() {
         instanceGroup.request = function(reqOpts, callback) {
@@ -196,7 +196,7 @@ describe('InstanceGroup', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {name: 'op-name'};
+      let apiResponse = {name: 'op-name'};
 
       beforeEach(function() {
         instanceGroup.request = function(reqOpts, callback) {
@@ -205,7 +205,7 @@ describe('InstanceGroup', function() {
       });
 
       it('should return an Operation and API response', function(done) {
-        var operation = {};
+        let operation = {};
 
         instanceGroup.zone.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -234,8 +234,8 @@ describe('InstanceGroup', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -260,7 +260,7 @@ describe('InstanceGroup', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -271,7 +271,7 @@ describe('InstanceGroup', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         instanceGroup.zone.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -312,7 +312,7 @@ describe('InstanceGroup', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       instanceGroup.request = function(reqOpts) {
         assert.strictEqual(reqOpts.method, 'POST');
@@ -327,7 +327,7 @@ describe('InstanceGroup', function() {
     });
 
     describe('options.running', function() {
-      var OPTIONS = {
+      let OPTIONS = {
         running: true,
       };
 
@@ -344,8 +344,8 @@ describe('InstanceGroup', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         instanceGroup.request = function(reqOpts, callback) {
@@ -365,7 +365,7 @@ describe('InstanceGroup', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{instance: 'vm-name'}],
       };
 
@@ -376,11 +376,11 @@ describe('InstanceGroup', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -398,7 +398,7 @@ describe('InstanceGroup', function() {
       });
 
       it('should execute callback with VMs & API response', function(done) {
-        var vm = {};
+        let vm = {};
 
         instanceGroup.zone.vm = function(name) {
           assert.strictEqual(name, apiResponse.items[0].instance);
@@ -420,7 +420,7 @@ describe('InstanceGroup', function() {
   });
 
   describe('remove', function() {
-    var VMS = [{url: 'vm-url'}, {url: 'vm-url-2'}];
+    let VMS = [{url: 'vm-url'}, {url: 'vm-url-2'}];
 
     it('should make the correct API request', function(done) {
       instanceGroup.request = function(reqOpts) {
@@ -441,8 +441,8 @@ describe('InstanceGroup', function() {
     });
 
     describe('error', function() {
-      var apiResponse = {};
-      var error = new Error('Error.');
+      let apiResponse = {};
+      let error = new Error('Error.');
 
       beforeEach(function() {
         instanceGroup.request = function(reqOpts, callback) {
@@ -461,7 +461,7 @@ describe('InstanceGroup', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {name: 'op-name'};
+      let apiResponse = {name: 'op-name'};
 
       beforeEach(function() {
         instanceGroup.request = function(reqOpts, callback) {
@@ -470,7 +470,7 @@ describe('InstanceGroup', function() {
       });
 
       it('should return an Operation and API response', function(done) {
-        var operation = {};
+        let operation = {};
 
         instanceGroup.zone.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -489,13 +489,13 @@ describe('InstanceGroup', function() {
   });
 
   describe('setPorts', function() {
-    var PORTS = {
+    let PORTS = {
       http: 80,
       https: 443,
     };
 
     it('should format the named ports', function(done) {
-      var expectedNamedPorts = [];
+      let expectedNamedPorts = [];
 
       InstanceGroup.formatPorts_ = function(ports) {
         assert.strictEqual(ports, PORTS);
@@ -513,8 +513,8 @@ describe('InstanceGroup', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         instanceGroup.request = function(reqOpts, callback) {
@@ -539,7 +539,7 @@ describe('InstanceGroup', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -550,7 +550,7 @@ describe('InstanceGroup', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         instanceGroup.zone.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/machine-type.js b/test/machine-type.js
index c1932144..986c52a3 100644
--- a/test/machine-type.js
+++ b/test/machine-type.js
@@ -16,10 +16,10 @@
 
 'use strict';
 
-var assert = require('assert');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
+let assert = require('assert');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
 
 function FakeServiceObject() {
   this.calledWith_ = arguments;
@@ -29,14 +29,14 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('MachineType', function() {
-  var MachineType;
-  var machineType;
-  var ZONE_NAME = 'zone-1';
-  var ZONE = {
+  let MachineType;
+  let machineType;
+  let ZONE_NAME = 'zone-1';
+  let ZONE = {
     name: ZONE_NAME,
   };
 
-  var MACHINE_TYPE_NAME = 'g1-small';
+  let MACHINE_TYPE_NAME = 'g1-small';
 
   before(function() {
     MachineType = proxyquire('../src/machine-type.js', {
@@ -62,7 +62,7 @@ describe('MachineType', function() {
     it('should inherit from ServiceObject', function() {
       assert(machineType instanceof ServiceObject);
 
-      var calledWith = machineType.calledWith_[0];
+      let calledWith = machineType.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, ZONE);
       assert.strictEqual(calledWith.baseUrl, '/machineTypes');
diff --git a/test/network.js b/test/network.js
index 0da515c7..b2e98750 100644
--- a/test/network.js
+++ b/test/network.js
@@ -16,16 +16,16 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var format = require('string-format-obj');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let assert = require('assert');
+let extend = require('extend');
+let format = require('string-format-obj');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class, options) {
     if (Class.name !== 'Network') {
       return;
@@ -44,23 +44,23 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Network', function() {
-  var Network;
-  var network;
+  let Network;
+  let network;
 
   /* eslint-disable no-unused-vars */
-  var REGION;
-  var Region;
+  let REGION;
+  let Region;
 
-  var COMPUTE = {
+  let COMPUTE = {
     projectId: 'project-id',
     createNetwork: util.noop,
   };
-  var NETWORK_NAME = 'network-name';
-  var NETWORK_FULL_NAME = format('projects/{pId}/global/networks/{name}', {
+  let NETWORK_NAME = 'network-name';
+  let NETWORK_FULL_NAME = format('projects/{pId}/global/networks/{name}', {
     pId: COMPUTE.projectId,
     name: NETWORK_NAME,
   });
-  var REGION_NAME = 'region-name';
+  let REGION_NAME = 'region-name';
 
   before(function() {
     Network = proxyquire('../src/network.js', {
@@ -92,8 +92,8 @@ describe('Network', function() {
     });
 
     it('should format the network name', function() {
-      var formatName_ = Network.formatName_;
-      var formattedName = 'projects/a/global/networks/b';
+      let formatName_ = Network.formatName_;
+      let formattedName = 'projects/a/global/networks/b';
 
       Network.formatName_ = function(compute, name) {
         Network.formatName_ = formatName_;
@@ -104,7 +104,7 @@ describe('Network', function() {
         return formattedName;
       };
 
-      var network = new Network(COMPUTE, NETWORK_NAME);
+      let network = new Network(COMPUTE, NETWORK_NAME);
       assert(network.formattedName, formattedName);
     });
 
@@ -118,10 +118,10 @@ describe('Network', function() {
         },
       });
 
-      var network = new Network(computeInstance, NETWORK_NAME);
+      let network = new Network(computeInstance, NETWORK_NAME);
       assert(network instanceof ServiceObject);
 
-      var calledWith = network.calledWith_[0];
+      let calledWith = network.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, computeInstance);
       assert.strictEqual(calledWith.baseUrl, '/global/networks');
@@ -137,16 +137,16 @@ describe('Network', function() {
 
   describe('formatName_', function() {
     it('should format the name', function() {
-      var formattedName_ = Network.formatName_(COMPUTE, NETWORK_NAME);
+      let formattedName_ = Network.formatName_(COMPUTE, NETWORK_NAME);
       assert.strictEqual(formattedName_, NETWORK_FULL_NAME);
     });
   });
 
   describe('createFirewall', function() {
     it('should make the correct call to Compute', function(done) {
-      var name = 'firewall-name';
-      var config = {a: 'b', c: 'd'};
-      var expectedConfig = extend({}, config, {
+      let name = 'firewall-name';
+      let config = {a: 'b', c: 'd'};
+      let expectedConfig = extend({}, config, {
         network: network.formattedName,
       });
 
@@ -162,15 +162,15 @@ describe('Network', function() {
 
   describe('createSubnetwork', function() {
     it('should call region.createSubnetwork correctly', function(done) {
-      var name = 'subnetwork-name';
-      var region = {};
-      var config = {
+      let name = 'subnetwork-name';
+      let region = {};
+      let config = {
         a: 'b',
         c: 'd',
         region: REGION_NAME,
       };
 
-      var expectedConfig = extend({}, config, {
+      let expectedConfig = extend({}, config, {
         network: network.formattedName,
       });
       delete expectedConfig.region;
@@ -202,8 +202,8 @@ describe('Network', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -228,7 +228,7 @@ describe('Network', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -239,7 +239,7 @@ describe('Network', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         network.compute.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -265,15 +265,15 @@ describe('Network', function() {
 
   describe('firewall', function() {
     it('should return a Firewall with the correct metadata', function() {
-      var name = 'firewall-name';
-      var firewall = {};
+      let name = 'firewall-name';
+      let firewall = {};
 
       network.compute.firewall = function(name_) {
         assert.strictEqual(name_, name);
         return firewall;
       };
 
-      var firewallInstance = network.firewall(name);
+      let firewallInstance = network.firewall(name);
       assert.deepStrictEqual(firewallInstance.metadata, {
         network: network.formattedName,
       });
@@ -282,8 +282,8 @@ describe('Network', function() {
 
   describe('getFirewalls', function() {
     it('should make the correct call to Compute', function(done) {
-      var options = {a: 'b', c: 'd'};
-      var expectedOptions = extend({}, options, {
+      let options = {a: 'b', c: 'd'};
+      let expectedOptions = extend({}, options, {
         filter: 'network eq .*' + network.formattedName,
       });
 
@@ -306,8 +306,8 @@ describe('Network', function() {
 
   describe('getFirewallsStream', function() {
     it('should call to getFirewallsStream correctly', function(done) {
-      var options = {a: 'b', c: 'd'};
-      var expectedOptions = extend({}, options, {
+      let options = {a: 'b', c: 'd'};
+      let expectedOptions = extend({}, options, {
         filter: 'network eq .*' + network.formattedName,
       });
 
@@ -328,22 +328,22 @@ describe('Network', function() {
     });
 
     it('should return a stream', function(done) {
-      var fakeStream = {};
+      let fakeStream = {};
 
       network.compute.getFirewallsStream = function() {
         setImmediate(done);
         return fakeStream;
       };
 
-      var stream = network.getFirewallsStream();
+      let stream = network.getFirewallsStream();
       assert.strictEqual(stream, fakeStream);
     });
   });
 
   describe('getSubnetworks', function() {
     it('should call to compute.getSubnetworks correctly', function(done) {
-      var options = {a: 'b', c: 'd'};
-      var expectedOptions = extend({}, options, {
+      let options = {a: 'b', c: 'd'};
+      let expectedOptions = extend({}, options, {
         filter: 'network eq .*' + network.formattedName,
       });
 
@@ -366,8 +366,8 @@ describe('Network', function() {
 
   describe('getSubnetworksStream', function() {
     it('should call to getSubnetworksStream correctly', function(done) {
-      var options = {a: 'b', c: 'd'};
-      var expectedOptions = extend({}, options, {
+      let options = {a: 'b', c: 'd'};
+      let expectedOptions = extend({}, options, {
         filter: 'network eq .*' + network.formattedName,
       });
 
@@ -388,14 +388,14 @@ describe('Network', function() {
     });
 
     it('should return a stream', function(done) {
-      var fakeStream = {};
+      let fakeStream = {};
 
       network.compute.getSubnetworksStream = function() {
         setImmediate(done);
         return fakeStream;
       };
 
-      var stream = network.getSubnetworksStream();
+      let stream = network.getSubnetworksStream();
       assert.strictEqual(stream, fakeStream);
     });
   });
diff --git a/test/operation.js b/test/operation.js
index f82086be..6a464298 100644
--- a/test/operation.js
+++ b/test/operation.js
@@ -16,10 +16,10 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var proxyquire = require('proxyquire').noPreserveCache();
-var util = require('@google-cloud/common').util;
+let assert = require('assert');
+let extend = require('extend');
+let proxyquire = require('proxyquire').noPreserveCache();
+let util = require('@google-cloud/common').util;
 
 function FakeOperation() {
   this.calledWith_ = arguments;
@@ -29,9 +29,9 @@ function FakeServiceObject() {
   this.calledWith_ = arguments;
 }
 
-var parseHttpRespBodyOverride = null;
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let parseHttpRespBodyOverride = null;
+let promisified = false;
+let fakeUtil = extend({}, util, {
   parseHttpRespBody: function() {
     if (parseHttpRespBodyOverride) {
       return parseHttpRespBodyOverride.apply(null, arguments);
@@ -47,13 +47,13 @@ var fakeUtil = extend({}, util, {
 });
 
 describe('Operation', function() {
-  var Operation;
-  var operation;
+  let Operation;
+  let operation;
 
-  var SCOPE = {
+  let SCOPE = {
     Promise: Promise,
   };
-  var OPERATION_NAME = 'operation-name';
+  let OPERATION_NAME = 'operation-name';
 
   before(function() {
     Operation = proxyquire('../src/operation.js', {
@@ -78,7 +78,7 @@ describe('Operation', function() {
     it('should inherit from Operation', function() {
       assert(operation instanceof FakeOperation);
 
-      var calledWith = operation.calledWith_[0];
+      let calledWith = operation.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, SCOPE);
       assert.strictEqual(calledWith.baseUrl, '/operations');
@@ -95,7 +95,7 @@ describe('Operation', function() {
     });
 
     it('should give the right baseUrl for a global Operation', function() {
-      var operation = new Operation(
+      let operation = new Operation(
         {
           constructor: {
             name: 'Compute',
@@ -104,7 +104,7 @@ describe('Operation', function() {
         OPERATION_NAME
       );
 
-      var calledWith = operation.calledWith_[0];
+      let calledWith = operation.calledWith_[0];
       assert.strictEqual(calledWith.baseUrl, '/global/operations');
     });
   });
@@ -120,8 +120,8 @@ describe('Operation', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.getMetadata = function(callback) {
@@ -130,7 +130,7 @@ describe('Operation', function() {
       });
 
       it('should ignore false errors', function(done) {
-        var apiResponse = {
+        let apiResponse = {
           name: operation.name,
           error: {
             errors: [],
@@ -166,7 +166,7 @@ describe('Operation', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {a: 'b', c: 'd'};
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.getMetadata = function(callback) {
@@ -213,7 +213,7 @@ describe('Operation', function() {
     });
 
     describe('API error', function() {
-      var error = new Error('Error.');
+      let error = new Error('Error.');
 
       beforeEach(function() {
         operation.getMetadata = function(callback) {
@@ -230,8 +230,8 @@ describe('Operation', function() {
     });
 
     describe('operation failure', function() {
-      var error = new Error('Error.');
-      var apiResponse = {error: error};
+      let error = new Error('Error.');
+      let apiResponse = {error: error};
 
       beforeEach(function() {
         operation.getMetadata = function(callback) {
@@ -240,7 +240,7 @@ describe('Operation', function() {
       });
 
       it('should parse and return the response body', function(done) {
-        var parsedHttpRespBody = {err: {}};
+        let parsedHttpRespBody = {err: {}};
 
         parseHttpRespBodyOverride = function(body) {
           assert.strictEqual(body, apiResponse);
@@ -255,7 +255,7 @@ describe('Operation', function() {
     });
 
     describe('operation running', function() {
-      var apiResponse = {status: 'RUNNING'};
+      let apiResponse = {status: 'RUNNING'};
 
       beforeEach(function() {
         operation.getMetadata = function(callback) {
@@ -296,7 +296,7 @@ describe('Operation', function() {
     });
 
     describe('operation complete', function() {
-      var apiResponse = {status: 'DONE'};
+      let apiResponse = {status: 'DONE'};
 
       beforeEach(function() {
         operation.getMetadata = function(callback) {
diff --git a/test/project.js b/test/project.js
index 1aadae04..ddb10cf2 100644
--- a/test/project.js
+++ b/test/project.js
@@ -16,13 +16,13 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var proxyquire = require('proxyquire');
-var util = require('@google-cloud/common').util;
+let assert = require('assert');
+let extend = require('extend');
+let proxyquire = require('proxyquire');
+let util = require('@google-cloud/common').util;
 
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Project') {
       promisified = true;
@@ -35,11 +35,11 @@ function FakeServiceObject() {
 }
 
 describe('Project', function() {
-  var Project;
-  var project;
+  let Project;
+  let project;
 
-  var PROJECT_ID = 'project-1';
-  var COMPUTE = {
+  let PROJECT_ID = 'project-1';
+  let COMPUTE = {
     projectId: PROJECT_ID,
     authConfig: {a: 'b', c: 'd'},
   };
@@ -69,7 +69,7 @@ describe('Project', function() {
     it('should inherit from ServiceObject', function() {
       assert(project instanceof FakeServiceObject);
 
-      var calledWith = project.calledWith_[0];
+      let calledWith = project.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, COMPUTE);
       assert.strictEqual(calledWith.baseUrl, '');
diff --git a/test/region.js b/test/region.js
index 3ed53829..ffe648bd 100644
--- a/test/region.js
+++ b/test/region.js
@@ -16,17 +16,17 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var assert = require('assert');
-var common = require('@google-cloud/common');
-var extend = require('extend');
-var is = require('is');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = common.ServiceObject;
-
-var promisified = false;
-var fakeUtil = extend({}, common.util, {
+let arrify = require('arrify');
+let assert = require('assert');
+let common = require('@google-cloud/common');
+let extend = require('extend');
+let is = require('is');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = common.ServiceObject;
+
+let promisified = false;
+let fakeUtil = extend({}, common.util, {
   promisifyAll: function(Class, options) {
     if (Class.name !== 'Region') {
       return;
@@ -69,8 +69,8 @@ function FakeSubnetwork() {
 
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
-var extended = false;
-var fakePaginator = {
+let extended = false;
+let fakePaginator = {
   extend: function(Class, methods) {
     if (Class.name !== 'Region') {
       return;
@@ -92,13 +92,13 @@ var fakePaginator = {
 };
 
 describe('Region', function() {
-  var Region;
-  var region;
+  let Region;
+  let region;
 
-  var COMPUTE = {
+  let COMPUTE = {
     authConfig: {a: 'b', c: 'd'},
   };
-  var REGION_NAME = 'us-central1';
+  let REGION_NAME = 'us-central1';
 
   before(function() {
     Region = proxyquire('../src/region.js', {
@@ -142,7 +142,7 @@ describe('Region', function() {
     it('should inherit from ServiceObject', function() {
       assert(region instanceof ServiceObject);
 
-      var calledWith = region.calledWith_[0];
+      let calledWith = region.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, COMPUTE);
       assert.strictEqual(calledWith.baseUrl, '/regions');
@@ -156,41 +156,41 @@ describe('Region', function() {
 
     describe('request interceptor', function() {
       it('should assign a request interceptor', function() {
-        var requestInterceptor = region.interceptors.pop().request;
+        let requestInterceptor = region.interceptors.pop().request;
         assert(is.fn(requestInterceptor));
       });
 
       it('should strip `/global` from forwardingRules requests', function() {
-        var reqOpts = {
+        let reqOpts = {
           uri: '/compute/v1/projects/projectId/global/forwardingRules',
         };
-        var expectedReqOpts = {
+        let expectedReqOpts = {
           uri: '/compute/v1/projects/projectId/forwardingRules',
         };
 
-        var requestInterceptor = region.interceptors.pop().request;
+        let requestInterceptor = region.interceptors.pop().request;
         assert.deepStrictEqual(requestInterceptor(reqOpts), expectedReqOpts);
       });
 
       it('should not affect non-cancel requests', function() {
-        var reqOpts = {
+        let reqOpts = {
           uri: '/compute/v1/projects/projectId/other/request',
         };
-        var expectedReqOpts = {
+        let expectedReqOpts = {
           uri: '/compute/v1/projects/projectId/other/request',
         };
 
-        var requestInterceptor = region.interceptors.pop().request;
+        let requestInterceptor = region.interceptors.pop().request;
         assert.deepStrictEqual(requestInterceptor(reqOpts), expectedReqOpts);
       });
     });
   });
 
   describe('address', function() {
-    var NAME = 'address-name';
+    let NAME = 'address-name';
 
     it('should return an Address object', function() {
-      var address = region.address(NAME);
+      let address = region.address(NAME);
       assert(address instanceof FakeAddress);
       assert.strictEqual(address.calledWith_[0], region);
       assert.strictEqual(address.calledWith_[1], NAME);
@@ -198,12 +198,12 @@ describe('Region', function() {
   });
 
   describe('createAddress', function() {
-    var NAME = 'address-name';
-    var OPTIONS = {a: 'b', c: 'd'};
-    var EXPECTED_BODY = extend({}, OPTIONS, {name: NAME});
+    let NAME = 'address-name';
+    let OPTIONS = {a: 'b', c: 'd'};
+    let EXPECTED_BODY = extend({}, OPTIONS, {name: NAME});
 
     it('should not require any options', function(done) {
-      var expectedBody = {name: NAME};
+      let expectedBody = {name: NAME};
 
       region.request = function(reqOpts) {
         assert.deepStrictEqual(reqOpts.json, expectedBody);
@@ -226,8 +226,8 @@ describe('Region', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         region.request = function(reqOpts, callback) {
@@ -247,7 +247,7 @@ describe('Region', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {name: 'operation-name'};
+      let apiResponse = {name: 'operation-name'};
 
       beforeEach(function() {
         region.request = function(reqOpts, callback) {
@@ -256,8 +256,8 @@ describe('Region', function() {
       });
 
       it('should exec callback with Address, Op & apiResponse', function(done) {
-        var address = {};
-        var operation = {};
+        let address = {};
+        let operation = {};
 
         region.address = function(name) {
           assert.strictEqual(name, NAME);
@@ -285,8 +285,8 @@ describe('Region', function() {
   });
 
   describe('createRule', function() {
-    var NAME = 'rule-name';
-    var CONFIG = {};
+    let NAME = 'rule-name';
+    let CONFIG = {};
 
     it('should call compute#createRule', function(done) {
       region.parent.createRule = function(name, config, callback) {
@@ -301,13 +301,13 @@ describe('Region', function() {
   });
 
   describe('createSubnetwork', function() {
-    var NAME = 'subnetwork-name';
-    var CONFIG = {
+    let NAME = 'subnetwork-name';
+    let CONFIG = {
       a: 'b',
       c: 'd',
       network: 'network-name',
     };
-    var EXPECTED_BODY = extend({}, CONFIG, {name: NAME});
+    let EXPECTED_BODY = extend({}, CONFIG, {name: NAME});
 
     it('should make the correct API request', function(done) {
       region.request = function(reqOpts) {
@@ -323,10 +323,10 @@ describe('Region', function() {
 
     describe('config.network', function() {
       it('should accept a Network object', function(done) {
-        var network = new FakeNetwork();
+        let network = new FakeNetwork();
         network.formattedName = 'formatted-name';
 
-        var config = extend({}, CONFIG, {
+        let config = extend({}, CONFIG, {
           network: network,
         });
 
@@ -341,7 +341,7 @@ describe('Region', function() {
 
     describe('config.range', function() {
       it('should accept and delete a range property', function(done) {
-        var config = extend({}, CONFIG, {
+        let config = extend({}, CONFIG, {
           range: '...',
         });
 
@@ -356,8 +356,8 @@ describe('Region', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         region.request = function(reqOpts, callback) {
@@ -377,7 +377,7 @@ describe('Region', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {name: 'operation-name'};
+      let apiResponse = {name: 'operation-name'};
 
       beforeEach(function() {
         region.request = function(reqOpts, callback) {
@@ -386,8 +386,8 @@ describe('Region', function() {
       });
 
       it('should exec cb with Subnetwork, Op & apiResponse', function(done) {
-        var subnetwork = {};
-        var operation = {};
+        let subnetwork = {};
+        let operation = {};
 
         region.subnetwork = function(name) {
           assert.strictEqual(name, NAME);
@@ -425,7 +425,7 @@ describe('Region', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       region.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/addresses');
@@ -438,8 +438,8 @@ describe('Region', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         region.request = function(reqOpts, callback) {
@@ -459,7 +459,7 @@ describe('Region', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{name: 'operation-name'}],
       };
 
@@ -470,11 +470,11 @@ describe('Region', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -492,7 +492,7 @@ describe('Region', function() {
       });
 
       it('should execute callback with Operations & API resp', function(done) {
-        var address = {};
+        let address = {};
 
         region.address = function(name) {
           assert.strictEqual(name, apiResponse.items[0].name);
@@ -524,7 +524,7 @@ describe('Region', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       region.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/operations');
@@ -537,8 +537,8 @@ describe('Region', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         region.request = function(reqOpts, callback) {
@@ -558,7 +558,7 @@ describe('Region', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{name: 'operation-name'}],
       };
 
@@ -569,11 +569,11 @@ describe('Region', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -591,7 +591,7 @@ describe('Region', function() {
       });
 
       it('should execute callback with Operations & API resp', function(done) {
-        var operation = {};
+        let operation = {};
 
         region.operation = function(name) {
           assert.strictEqual(name, apiResponse.items[0].name);
@@ -623,7 +623,7 @@ describe('Region', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       region.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/forwardingRules');
@@ -636,8 +636,8 @@ describe('Region', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         region.request = function(reqOpts, callback) {
@@ -657,7 +657,7 @@ describe('Region', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{name: 'operation-name'}],
       };
 
@@ -668,11 +668,11 @@ describe('Region', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -690,7 +690,7 @@ describe('Region', function() {
       });
 
       it('should execute callback with Operations & API resp', function(done) {
-        var rule = {};
+        let rule = {};
 
         region.rule = function(name) {
           assert.strictEqual(name, apiResponse.items[0].name);
@@ -722,7 +722,7 @@ describe('Region', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       region.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/subnetworks');
@@ -735,8 +735,8 @@ describe('Region', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         region.request = function(reqOpts, callback) {
@@ -756,7 +756,7 @@ describe('Region', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{name: 'subnetwork-name'}],
       };
 
@@ -767,11 +767,11 @@ describe('Region', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -789,7 +789,7 @@ describe('Region', function() {
       });
 
       it('should execute callback with Operations & API resp', function(done) {
-        var subnetwork = {};
+        let subnetwork = {};
 
         region.subnetwork = function(name) {
           assert.strictEqual(name, apiResponse.items[0].name);
@@ -811,10 +811,10 @@ describe('Region', function() {
   });
 
   describe('operation', function() {
-    var NAME = 'operation-name';
+    let NAME = 'operation-name';
 
     it('should return a Operation object', function() {
-      var operation = region.operation(NAME);
+      let operation = region.operation(NAME);
       assert(operation instanceof FakeOperation);
       assert.strictEqual(operation.calledWith_[0], region);
       assert.strictEqual(operation.calledWith_[1], NAME);
@@ -822,10 +822,10 @@ describe('Region', function() {
   });
 
   describe('rule', function() {
-    var NAME = 'rule-name';
+    let NAME = 'rule-name';
 
     it('should return a Operation object', function() {
-      var rule = region.rule(NAME);
+      let rule = region.rule(NAME);
       assert(rule instanceof FakeRule);
       assert.strictEqual(rule.calledWith_[0], region);
       assert.strictEqual(rule.calledWith_[1], NAME);
@@ -833,10 +833,10 @@ describe('Region', function() {
   });
 
   describe('subnetwork', function() {
-    var NAME = 'subnetwork-name';
+    let NAME = 'subnetwork-name';
 
     it('should return a Subnetwork object', function() {
-      var subnetwork = region.subnetwork(NAME);
+      let subnetwork = region.subnetwork(NAME);
       assert(subnetwork instanceof FakeSubnetwork);
       assert.strictEqual(subnetwork.calledWith_[0], region);
       assert.strictEqual(subnetwork.calledWith_[1], NAME);
diff --git a/test/rule.js b/test/rule.js
index 2866b2d2..5bdcc11b 100644
--- a/test/rule.js
+++ b/test/rule.js
@@ -16,13 +16,13 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var proxyquire = require('proxyquire');
-var util = require('@google-cloud/common').util;
+let assert = require('assert');
+let extend = require('extend');
+let proxyquire = require('proxyquire');
+let util = require('@google-cloud/common').util;
 
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Rule') {
       promisified = true;
@@ -35,16 +35,16 @@ function FakeServiceObject() {
 }
 
 describe('Rule', function() {
-  var Rule;
-  var rule;
+  let Rule;
+  let rule;
 
   function Compute() {
     this.createRule = util.noop;
     this.operation = util.noop;
   }
 
-  var COMPUTE = new Compute();
-  var RULE_NAME = 'rule-name';
+  let COMPUTE = new Compute();
+  let RULE_NAME = 'rule-name';
 
   before(function() {
     Rule = proxyquire('../src/rule.js', {
@@ -61,8 +61,8 @@ describe('Rule', function() {
 
   describe('instantiation', function() {
     it('should inherit from ServiceObject', function() {
-      var computeInstance = new Compute();
-      var bindMethod = {};
+      let computeInstance = new Compute();
+      let bindMethod = {};
 
       extend(computeInstance, {
         createRule: {
@@ -73,10 +73,10 @@ describe('Rule', function() {
         },
       });
 
-      var rule = new Rule(computeInstance, RULE_NAME);
+      let rule = new Rule(computeInstance, RULE_NAME);
       assert(rule instanceof FakeServiceObject);
 
-      var calledWith = rule.calledWith_[0];
+      let calledWith = rule.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, computeInstance);
       assert.strictEqual(calledWith.baseUrl, '/global/forwardingRules');
@@ -95,10 +95,10 @@ describe('Rule', function() {
     });
 
     it('should not use global forwarding rules', function() {
-      var rule = new Rule({createRule: util.noop}, RULE_NAME);
+      let rule = new Rule({createRule: util.noop}, RULE_NAME);
       assert(rule instanceof FakeServiceObject);
 
-      var calledWith = rule.calledWith_[0];
+      let calledWith = rule.calledWith_[0];
 
       assert.strictEqual(calledWith.baseUrl, '/forwardingRules');
     });
@@ -119,8 +119,8 @@ describe('Rule', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -145,7 +145,7 @@ describe('Rule', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -156,7 +156,7 @@ describe('Rule', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         rule.scope.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -181,7 +181,7 @@ describe('Rule', function() {
   });
 
   describe('setTarget', function() {
-    var TARGET = 'target';
+    let TARGET = 'target';
 
     it('should make the correct API request', function(done) {
       rule.request = function(reqOpts) {
@@ -196,8 +196,8 @@ describe('Rule', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {};
+      let error = new Error('Error.');
+      let apiResponse = {};
 
       beforeEach(function() {
         rule.request = function(reqOpts, callback) {
@@ -216,7 +216,7 @@ describe('Rule', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -227,7 +227,7 @@ describe('Rule', function() {
       });
 
       it('should execute callback with operation & response', function(done) {
-        var operation = {};
+        let operation = {};
 
         rule.scope.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/service.js b/test/service.js
index 824e740b..822cea22 100644
--- a/test/service.js
+++ b/test/service.js
@@ -16,15 +16,15 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let assert = require('assert');
+let extend = require('extend');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Service') {
       promisified = true;
@@ -40,12 +40,12 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Service', function() {
-  var Service;
-  var service;
+  let Service;
+  let service;
 
-  var SERVICE_NAME = 'service-name';
+  let SERVICE_NAME = 'service-name';
 
-  var COMPUTE = {
+  let COMPUTE = {
     projectId: 'project-id',
     createService: util.noop,
   };
@@ -77,7 +77,7 @@ describe('Service', function() {
     });
 
     it('should inherit from ServiceObject', function() {
-      var createMethod = util.noop;
+      let createMethod = util.noop;
 
       var computeInstance = extend({}, COMPUTE, {
         createService: {
@@ -88,10 +88,10 @@ describe('Service', function() {
         },
       });
 
-      var service = new Service(computeInstance, SERVICE_NAME);
+      let service = new Service(computeInstance, SERVICE_NAME);
       assert(service instanceof ServiceObject);
 
-      var calledWith = service.calledWith_[0];
+      let calledWith = service.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, computeInstance);
       assert.strictEqual(calledWith.baseUrl, '/global/backendServices');
@@ -117,8 +117,8 @@ describe('Service', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -143,7 +143,7 @@ describe('Service', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -154,7 +154,7 @@ describe('Service', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         service.compute.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
@@ -179,7 +179,7 @@ describe('Service', function() {
   });
 
   describe('getHealth', function() {
-    var GROUP = 'http://group-url';
+    let GROUP = 'http://group-url';
 
     it('should make the correct request', function(done) {
       service.request = function(reqOpts) {
@@ -197,7 +197,7 @@ describe('Service', function() {
 
     describe('group object', function() {
       it('should compose the right URL', function(done) {
-        var group = {
+        let group = {
           name: 'instance-group-name',
           zone: 'zone-name',
         };
@@ -221,7 +221,7 @@ describe('Service', function() {
       });
 
       it('should compose the right URL', function(done) {
-        var group = {
+        let group = {
           name: 'instance-group-name',
           // Simulating a {module:compute/zone}:
           zone: {
@@ -249,8 +249,8 @@ describe('Service', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         service.request = function(reqOpts, callback) {
@@ -269,7 +269,7 @@ describe('Service', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         healthStatus: {},
       };
 
@@ -292,7 +292,7 @@ describe('Service', function() {
 
   describe('setMetadata', function() {
     it('should make the correct API request', function(done) {
-      var metadata = {};
+      let metadata = {};
 
       service.request = function(reqOpts) {
         assert.strictEqual(reqOpts.method, 'PATCH');
@@ -306,8 +306,8 @@ describe('Service', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         service.request = function(reqOpts, callback) {
@@ -326,7 +326,7 @@ describe('Service', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -337,8 +337,8 @@ describe('Service', function() {
       });
 
       it('should execute callback with operation & response', function(done) {
-        var operation = {};
-        var metadata = {a: 'b'};
+        let operation = {};
+        let metadata = {a: 'b'};
 
         service.compute.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/snapshot.js b/test/snapshot.js
index 54c09ba3..783b0c5e 100644
--- a/test/snapshot.js
+++ b/test/snapshot.js
@@ -16,15 +16,15 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var common = require('@google-cloud/common');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = common.ServiceObject;
-
-var promisified = false;
-var fakeUtil = extend({}, common.util, {
+let assert = require('assert');
+let extend = require('extend');
+let common = require('@google-cloud/common');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = common.ServiceObject;
+
+let promisified = false;
+let fakeUtil = extend({}, common.util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Snapshot') {
       promisified = true;
@@ -40,11 +40,11 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Snapshot', function() {
-  var Snapshot;
-  var snapshot;
+  let Snapshot;
+  let snapshot;
 
-  var COMPUTE = {};
-  var SNAPSHOT_NAME = 'snapshot-name';
+  let COMPUTE = {};
+  let SNAPSHOT_NAME = 'snapshot-name';
 
   before(function() {
     Snapshot = proxyquire('../src/snapshot.js', {
@@ -69,7 +69,7 @@ describe('Snapshot', function() {
     });
 
     it('should inherit from ServiceObject', function() {
-      var calledWith = snapshot.calledWith_[0];
+      let calledWith = snapshot.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, COMPUTE);
       assert.strictEqual(
@@ -99,10 +99,10 @@ describe('Snapshot', function() {
         },
       };
 
-      var snapshot = new Snapshot(scope, SNAPSHOT_NAME);
+      let snapshot = new Snapshot(scope, SNAPSHOT_NAME);
       assert(snapshot instanceof ServiceObject);
 
-      var calledWith = snapshot.calledWith_[0];
+      let calledWith = snapshot.calledWith_[0];
       assert.strictEqual(calledWith.methods.create, true);
 
       calledWith.createMethod(); // (scope.createSnapshot)
@@ -120,8 +120,8 @@ describe('Snapshot', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -146,7 +146,7 @@ describe('Snapshot', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {name: 'operation-name'};
+      let apiResponse = {name: 'operation-name'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.delete = function(callback) {
@@ -155,7 +155,7 @@ describe('Snapshot', function() {
       });
 
       it('should exec callback with Operation & API response', function(done) {
-        var operation = {};
+        let operation = {};
 
         snapshot.compute.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/subnetwork.js b/test/subnetwork.js
index 3948fc41..e3826389 100644
--- a/test/subnetwork.js
+++ b/test/subnetwork.js
@@ -16,15 +16,15 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let assert = require('assert');
+let extend = require('extend');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'Subnetwork') {
       promisified = true;
@@ -40,12 +40,12 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('Subnetwork', function() {
-  var Subnetwork;
-  var subnetwork;
+  let Subnetwork;
+  let subnetwork;
 
-  var SUBNETWORK_NAME = 'subnetwork_name';
-  var REGION_NAME = 'region-1';
-  var REGION = {
+  let SUBNETWORK_NAME = 'subnetwork_name';
+  let REGION_NAME = 'region-1';
+  let REGION = {
     createSubnetwork: util.noop,
     name: REGION_NAME,
   };
@@ -73,7 +73,7 @@ describe('Subnetwork', function() {
     });
 
     it('should inherit from ServiceObject', function() {
-      var createSubnetworkBound = {};
+      let createSubnetworkBound = {};
 
       var regionInstance = extend({}, REGION, {
         createSubnetwork: {
@@ -84,10 +84,10 @@ describe('Subnetwork', function() {
         },
       });
 
-      var subnetwork = new Subnetwork(regionInstance, SUBNETWORK_NAME);
+      let subnetwork = new Subnetwork(regionInstance, SUBNETWORK_NAME);
       assert(subnetwork instanceof ServiceObject);
 
-      var calledWith = subnetwork.calledWith_[0];
+      let calledWith = subnetwork.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, regionInstance);
       assert.strictEqual(calledWith.baseUrl, '/subnetworks');
@@ -118,8 +118,8 @@ describe('Subnetwork', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         subnetwork.request = function(reqOpts, callback) {
@@ -144,7 +144,7 @@ describe('Subnetwork', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         name: 'op-name',
       };
 
@@ -155,7 +155,7 @@ describe('Subnetwork', function() {
       });
 
       it('should execute callback with Operation & Response', function(done) {
-        var operation = {};
+        let operation = {};
 
         subnetwork.region.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/vm.js b/test/vm.js
index b4d38f65..a904dc78 100644
--- a/test/vm.js
+++ b/test/vm.js
@@ -16,17 +16,17 @@
 
 'use strict';
 
-var assert = require('assert');
-var extend = require('extend');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
+let assert = require('assert');
+let extend = require('extend');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
 
-var utilCached = extend({}, util);
+let utilCached = extend({}, util);
 
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class) {
     if (Class.name === 'VM') {
       promisified = true;
@@ -42,26 +42,26 @@ function FakeServiceObject() {
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
 describe('VM', function() {
-  var VM;
-  var vm;
+  let VM;
+  let vm;
 
-  var Disk;
-  var DISK;
+  let Disk;
+  let DISK;
 
-  var COMPUTE = {
+  let COMPUTE = {
     authClient: {
       projectId: 'project-id',
     },
     projectId: 'project-id',
   };
-  var ZONE = {
+  let ZONE = {
     compute: COMPUTE,
     name: 'us-central1-a',
     createDisk: util.noop,
     createVM: util.noop,
   };
-  var VM_NAME = 'vm-name';
-  var FULLY_QUALIFIED_NAME = [
+  let VM_NAME = 'vm-name';
+  let FULLY_QUALIFIED_NAME = [
     'project/project-id/zones/zone-name/instances/',
     VM_NAME,
   ].join('');
@@ -96,7 +96,7 @@ describe('VM', function() {
     });
 
     it('should strip a qualified name to just the instance name', function() {
-      var vm = new VM(ZONE, FULLY_QUALIFIED_NAME);
+      let vm = new VM(ZONE, FULLY_QUALIFIED_NAME);
       assert.strictEqual(vm.name, VM_NAME);
     });
 
@@ -132,10 +132,10 @@ describe('VM', function() {
         },
       });
 
-      var vm = new VM(zoneInstance, VM_NAME);
+      let vm = new VM(zoneInstance, VM_NAME);
       assert(vm instanceof ServiceObject);
 
-      var calledWith = vm.calledWith_[0];
+      let calledWith = vm.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, zoneInstance);
       assert.strictEqual(calledWith.baseUrl, '/instances');
@@ -150,8 +150,8 @@ describe('VM', function() {
   });
 
   describe('attachDisk', function() {
-    var CONFIG = {};
-    var EXPECTED_BODY;
+    let CONFIG = {};
+    let EXPECTED_BODY;
 
     beforeEach(function() {
       EXPECTED_BODY = {
@@ -184,7 +184,7 @@ describe('VM', function() {
       var CONFIG = extend({}, CONFIG, {readOnly: true});
 
       it('should set the correct mode', function(done) {
-        var expectedBody = extend({}, EXPECTED_BODY, {mode: 'READ_ONLY'});
+        let expectedBody = extend({}, EXPECTED_BODY, {mode: 'READ_ONLY'});
 
         vm.request = function(reqOpts) {
           assert.deepStrictEqual(reqOpts.json, expectedBody);
@@ -242,8 +242,8 @@ describe('VM', function() {
   });
 
   describe('detachDisk', function() {
-    var DEVICE_NAME;
-    var METADATA;
+    let DEVICE_NAME;
+    let METADATA;
 
     beforeEach(function() {
       DEVICE_NAME = DISK.formattedName;
@@ -274,7 +274,7 @@ describe('VM', function() {
     });
 
     it('should replace projectId token in disk name', function(done) {
-      var REPLACED_DEVICE_NAME = 'replaced-device-name';
+      let REPLACED_DEVICE_NAME = 'replaced-device-name';
 
       fakeUtil.replaceProjectIdToken = function(value, projectId) {
         assert.strictEqual(value, DISK.formattedName);
@@ -283,7 +283,7 @@ describe('VM', function() {
       };
 
       vm.getMetadata = function(callback) {
-        var metadata = {
+        let metadata = {
           disks: [
             {
               source: REPLACED_DEVICE_NAME,
@@ -304,7 +304,7 @@ describe('VM', function() {
     });
 
     it('should return an error if device name not found', function(done) {
-      var metadata = {
+      let metadata = {
         disks: [
           {
             source: 'a',
@@ -320,7 +320,7 @@ describe('VM', function() {
       vm.detachDisk(DISK, function(err) {
         assert.strictEqual(err.name, 'DetachDiskError');
 
-        var errorMessage = 'Device name for this disk was not found.';
+        let errorMessage = 'Device name for this disk was not found.';
         assert.strictEqual(err.message, errorMessage);
 
         done();
@@ -352,7 +352,7 @@ describe('VM', function() {
 
     describe('refreshing metadata', function() {
       describe('error', function() {
-        var ERROR = new Error('Error.');
+        let ERROR = new Error('Error.');
 
         beforeEach(function() {
           vm.getMetadata = function(callback) {
@@ -372,7 +372,7 @@ describe('VM', function() {
   });
 
   describe('getSerialPortOutput', function() {
-    var EXPECTED_QUERY = {port: 1};
+    let EXPECTED_QUERY = {port: 1};
 
     it('should default to port 1', function(done) {
       FakeServiceObject.prototype.request = function(reqOpts) {
@@ -384,7 +384,7 @@ describe('VM', function() {
     });
 
     it('should override the default port', function(done) {
-      var port = 8001;
+      let port = 8001;
 
       FakeServiceObject.prototype.request = function(reqOpts) {
         assert.strictEqual(reqOpts.qs.port, port);
@@ -406,8 +406,8 @@ describe('VM', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.request = function(reqOpts, callback) {
@@ -427,7 +427,7 @@ describe('VM', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {contents: 'contents'};
+      let apiResponse = {contents: 'contents'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.request = function(reqOpts, callback) {
@@ -457,8 +457,8 @@ describe('VM', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         vm.getMetadata = function(callback) {
@@ -479,14 +479,14 @@ describe('VM', function() {
     });
 
     describe('success', function() {
-      var metadata = {
+      let metadata = {
         tags: {
           items: [],
           fingerprint: 'fingerprint',
         },
       };
 
-      var apiResponse = {a: 'b', c: 'd'};
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         vm.getMetadata = function(callback) {
@@ -533,7 +533,7 @@ describe('VM', function() {
   });
 
   describe('resize', function() {
-    var MACHINE_TYPE = 'zones/' + ZONE.name + '/machineTypes/machineType';
+    let MACHINE_TYPE = 'zones/' + ZONE.name + '/machineTypes/machineType';
 
     beforeEach(function() {
       vm.request = util.noop;
@@ -557,7 +557,7 @@ describe('VM', function() {
     });
 
     it('should allow a partial machine type', function(done) {
-      var partialMachineType = MACHINE_TYPE.split('/').pop();
+      let partialMachineType = MACHINE_TYPE.split('/').pop();
 
       vm.request = function(reqOpts) {
         assert.strictEqual(reqOpts.method, 'POST');
@@ -573,7 +573,7 @@ describe('VM', function() {
 
     describe('error', function() {
       describe('instance is running', function() {
-        var error = new Error('Instance is starting or running.');
+        let error = new Error('Instance is starting or running.');
 
         beforeEach(function() {
           vm.zone.parent.execAfterOperation_ = function(callback) {
@@ -591,8 +591,8 @@ describe('VM', function() {
         });
 
         describe('stopping failed', function() {
-          var vmStopError = new Error('Error.');
-          var apiResponse = {};
+          let vmStopError = new Error('Error.');
+          let apiResponse = {};
 
           beforeEach(function() {
             // First: vm.request()
@@ -652,8 +652,8 @@ describe('VM', function() {
       });
 
       describe('instance is stopped', function() {
-        var error = new Error('Error');
-        var apiResponse = {};
+        let error = new Error('Error');
+        let apiResponse = {};
 
         beforeEach(function() {
           vm.zone.parent.execAfterOperation_ = function(callback) {
@@ -697,7 +697,7 @@ describe('VM', function() {
     });
 
     it('should not start the VM by request', function(done) {
-      var apiResponse = {};
+      let apiResponse = {};
 
       vm.zone.parent.execAfterOperation_ = function(callback) {
         callback(null, apiResponse);
@@ -716,14 +716,14 @@ describe('VM', function() {
   });
 
   describe('setMetadata', function() {
-    var METADATA = {
+    let METADATA = {
       newKey: 'newValue',
     };
 
     describe('getting the current fingerprint', function() {
       describe('error', function() {
-        var error = new Error('Error.');
-        var apiResponse = {};
+        let error = new Error('Error.');
+        let apiResponse = {};
 
         beforeEach(function() {
           vm.getMetadata = function(callback) {
@@ -742,13 +742,13 @@ describe('VM', function() {
         });
 
         describe('success', function() {
-          var metadata = {
+          let metadata = {
             metadata: {
               fingerprint: '===',
             },
           };
 
-          var apiResponse = {};
+          let apiResponse = {};
 
           beforeEach(function() {
             vm.getMetadata = function(callback) {
@@ -757,7 +757,7 @@ describe('VM', function() {
           });
 
           it('should make the correct request', function(done) {
-            var expectedNewMetadata = extend(true, {}, metadata.metadata, {
+            let expectedNewMetadata = extend(true, {}, metadata.metadata, {
               items: [
                 {
                   key: 'newKey',
@@ -782,8 +782,8 @@ describe('VM', function() {
   });
 
   describe('setTags', function() {
-    var TAGS = [];
-    var FINGERPRINT = '';
+    let TAGS = [];
+    let FINGERPRINT = '';
 
     it('should make the correct request', function(done) {
       vm.request = function(reqOpts, callback) {
@@ -857,7 +857,7 @@ describe('VM', function() {
   });
 
   describe('waitFor', function() {
-    var VALID_STATUSES = [
+    let VALID_STATUSES = [
       'PROVISIONING',
       'STAGING',
       'RUNNING',
@@ -901,10 +901,10 @@ describe('VM', function() {
     });
 
     it('should create a waiter', function(done) {
-      var now = new Date() / 1000;
+      let now = new Date() / 1000;
       vm.waitFor(VALID_STATUSES[0], done);
 
-      var createdWaiter = vm.waiters.pop();
+      let createdWaiter = vm.waiters.pop();
 
       assert.strictEqual(createdWaiter.status, VALID_STATUSES[0]);
       assert.strictEqual(createdWaiter.timeout, 300);
@@ -940,7 +940,7 @@ describe('VM', function() {
   });
 
   describe('startPolling_', function() {
-    var METADATA = {};
+    let METADATA = {};
 
     beforeEach(function() {
       vm.hasActiveWaiters = true;
@@ -970,7 +970,7 @@ describe('VM', function() {
     });
 
     describe('metadata refresh error', function() {
-      var ERROR = new Error('Error.');
+      let ERROR = new Error('Error.');
 
       beforeEach(function() {
         vm.getMetadata = function(callback) {
@@ -1005,8 +1005,8 @@ describe('VM', function() {
     });
 
     describe('desired status reached', function() {
-      var STATUS = 'status';
-      var METADATA = {
+      let STATUS = 'status';
+      let METADATA = {
         status: STATUS,
       };
 
@@ -1045,7 +1045,7 @@ describe('VM', function() {
     });
 
     describe('timeout exceeded', function() {
-      var STATUS = 'status';
+      let STATUS = 'status';
 
       beforeEach(function() {
         vm.waiters.push({
@@ -1087,8 +1087,8 @@ describe('VM', function() {
     });
 
     describe('desired status not reached yet', function() {
-      var STATUS = 'status';
-      var setTimeout = global.setTimeout;
+      let STATUS = 'status';
+      let setTimeout = global.setTimeout;
 
       beforeEach(function() {
         vm.waiters.push({
@@ -1123,7 +1123,7 @@ describe('VM', function() {
 
   describe('request', function() {
     it('should make the correct request to Compute', function(done) {
-      var reqOpts = {};
+      let reqOpts = {};
 
       FakeServiceObject.prototype.request = function(reqOpts_) {
         assert.strictEqual(this, vm);
@@ -1136,8 +1136,8 @@ describe('VM', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.request = function(reqOpts, callback) {
@@ -1156,7 +1156,7 @@ describe('VM', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {name: 'operation-name'};
+      let apiResponse = {name: 'operation-name'};
 
       beforeEach(function() {
         FakeServiceObject.prototype.request = function(reqOpts, callback) {
@@ -1165,7 +1165,7 @@ describe('VM', function() {
       });
 
       it('should execute callback with Zone object & API resp', function(done) {
-        var operation = {};
+        let operation = {};
 
         vm.zone.operation = function(name) {
           assert.strictEqual(name, apiResponse.name);
diff --git a/test/zone.js b/test/zone.js
index 5d7e0e04..cd041edf 100644
--- a/test/zone.js
+++ b/test/zone.js
@@ -16,17 +16,17 @@
 
 'use strict';
 
-var arrify = require('arrify');
-var assert = require('assert');
-var extend = require('extend');
-var gceImages = require('gce-images');
-var nodeutil = require('util');
-var proxyquire = require('proxyquire');
-var ServiceObject = require('@google-cloud/common').ServiceObject;
-var util = require('@google-cloud/common').util;
-
-var promisified = false;
-var fakeUtil = extend({}, util, {
+let arrify = require('arrify');
+let assert = require('assert');
+let extend = require('extend');
+let gceImages = require('gce-images');
+let nodeutil = require('util');
+let proxyquire = require('proxyquire');
+let ServiceObject = require('@google-cloud/common').ServiceObject;
+let util = require('@google-cloud/common').util;
+
+let promisified = false;
+let fakeUtil = extend({}, util, {
   promisifyAll: function(Class, options) {
     if (Class.name !== 'Zone') {
       return;
@@ -44,7 +44,7 @@ var fakeUtil = extend({}, util, {
   },
 });
 
-var gceImagesOverride;
+let gceImagesOverride;
 function fakeGceImages() {
   return (gceImagesOverride || gceImages).apply(null, arguments);
 }
@@ -57,7 +57,7 @@ function FakeDisk() {
   this.calledWith_ = [].slice.call(arguments);
 }
 
-var formatPortsOverride;
+let formatPortsOverride;
 FakeInstanceGroup.formatPorts_ = function() {
   return (formatPortsOverride || util.noop).apply(null, arguments);
 };
@@ -85,8 +85,8 @@ function FakeServiceObject() {
 
 nodeutil.inherits(FakeServiceObject, ServiceObject);
 
-var extended = false;
-var fakePaginator = {
+let extended = false;
+let fakePaginator = {
   extend: function(Class, methods) {
     if (Class.name !== 'Zone') {
       return;
@@ -110,14 +110,14 @@ var fakePaginator = {
 };
 
 describe('Zone', function() {
-  var Zone;
-  var zone;
+  let Zone;
+  let zone;
 
-  var COMPUTE = {
+  let COMPUTE = {
     authClient: {},
     projectId: 'project-id',
   };
-  var ZONE_NAME = 'us-central1-a';
+  let ZONE_NAME = 'us-central1-a';
 
   before(function() {
     Zone = proxyquire('../src/zone.js', {
@@ -169,21 +169,21 @@ describe('Zone', function() {
     });
 
     it('should create a gceImages instance', function() {
-      var gceVal = 'ok';
+      let gceVal = 'ok';
 
       gceImagesOverride = function(authConfig) {
         assert.strictEqual(authConfig.authClient, COMPUTE.authClient);
         return gceVal;
       };
 
-      var newZone = new Zone(COMPUTE, ZONE_NAME);
+      let newZone = new Zone(COMPUTE, ZONE_NAME);
       assert.strictEqual(newZone.gceImages, gceVal);
     });
 
     it('should inherit from ServiceObject', function() {
       assert(zone instanceof ServiceObject);
 
-      var calledWith = zone.calledWith_[0];
+      let calledWith = zone.calledWith_[0];
 
       assert.strictEqual(calledWith.parent, COMPUTE);
       assert.strictEqual(calledWith.baseUrl, '/zones');
@@ -197,10 +197,10 @@ describe('Zone', function() {
   });
 
   describe('autoscaler', function() {
-    var NAME = 'autoscaler-name';
+    let NAME = 'autoscaler-name';
 
     it('should return an Autoscaler object', function() {
-      var autoscaler = zone.autoscaler(NAME);
+      let autoscaler = zone.autoscaler(NAME);
       assert(autoscaler instanceof FakeAutoscaler);
       assert.strictEqual(autoscaler.calledWith_[0], zone);
       assert.strictEqual(autoscaler.calledWith_[1], NAME);
@@ -208,8 +208,8 @@ describe('Zone', function() {
   });
 
   describe('createAutoscaler', function() {
-    var NAME = 'autoscaler-name';
-    var TARGET = 'target';
+    let NAME = 'autoscaler-name';
+    let TARGET = 'target';
 
     beforeEach(function() {
       zone.request = util.noop;
@@ -222,7 +222,7 @@ describe('Zone', function() {
     });
 
     it('should make the correct request', function(done) {
-      var config = {
+      let config = {
         target: TARGET,
       };
 
@@ -235,7 +235,7 @@ describe('Zone', function() {
     });
 
     it('should use a provided autoscalingPolicy', function(done) {
-      var config = {
+      let config = {
         autoscalingPolicy: {
           a: 'b',
           c: 'd',
@@ -244,7 +244,7 @@ describe('Zone', function() {
       };
 
       zone.request = function(reqOpts) {
-        var policy = reqOpts.json.autoscalingPolicy;
+        let policy = reqOpts.json.autoscalingPolicy;
         assert.deepStrictEqual(policy, config.autoscalingPolicy);
         done();
       };
@@ -254,7 +254,7 @@ describe('Zone', function() {
 
     describe('config.target', function() {
       it('should use a provided http target', function(done) {
-        var config = {
+        let config = {
           target: 'http://my-target',
         };
 
@@ -267,7 +267,7 @@ describe('Zone', function() {
       });
 
       it('should use a provided https target', function(done) {
-        var config = {
+        let config = {
           target: 'https://my-target',
         };
 
@@ -280,12 +280,12 @@ describe('Zone', function() {
       });
 
       it('should create a full target URL', function(done) {
-        var config = {
+        let config = {
           target: 'my-target',
         };
 
         zone.request = function(reqOpts) {
-          var expectedTarget = [
+          let expectedTarget = [
             'https://content.googleapis.com/compute/v1/projects/',
             COMPUTE.projectId,
             '/zones/',
@@ -305,13 +305,13 @@ describe('Zone', function() {
 
     describe('config.coolDown', function() {
       it('should set coolDownPeriodSec', function(done) {
-        var config = {
+        let config = {
           coolDown: 80,
           target: TARGET,
         };
 
         zone.request = function(reqOpts) {
-          var policy = reqOpts.json.autoscalingPolicy;
+          let policy = reqOpts.json.autoscalingPolicy;
           assert.strictEqual(policy.coolDownPeriodSec, config.coolDown);
           assert.strictEqual(reqOpts.coolDown, undefined);
           done();
@@ -323,14 +323,14 @@ describe('Zone', function() {
 
     describe('config.cpu', function() {
       it('should set cpuUtilization', function(done) {
-        var config = {
+        let config = {
           cpu: 80,
           target: TARGET,
         };
 
         zone.request = function(reqOpts) {
-          var policy = reqOpts.json.autoscalingPolicy;
-          var cpu = policy.cpuUtilization;
+          let policy = reqOpts.json.autoscalingPolicy;
+          let cpu = policy.cpuUtilization;
           assert.strictEqual(cpu.utilizationTarget, config.cpu / 100);
           assert.strictEqual(reqOpts.cpu, undefined);
           done();
@@ -342,14 +342,14 @@ describe('Zone', function() {
 
     describe('config.loadBalance', function() {
       it('should set loadBalancingUtilization', function(done) {
-        var config = {
+        let config = {
           loadBalance: 80,
           target: TARGET,
         };
 
         zone.request = function(reqOpts) {
-          var policy = reqOpts.json.autoscalingPolicy;
-          var lb = policy.loadBalancingUtilization;
+          let policy = reqOpts.json.autoscalingPolicy;
+          let lb = policy.loadBalancingUtilization;
           assert.strictEqual(lb.utilizationTarget, config.loadBalance / 100);
           assert.strictEqual(reqOpts.loadBalance, undefined);
           done();
@@ -361,13 +361,13 @@ describe('Zone', function() {
 
     describe('config.maxReplicas', function() {
       it('should set maxNumReplicas', function(done) {
-        var config = {
+        let config = {
           maxReplicas: 10,
           target: TARGET,
         };
 
         zone.request = function(reqOpts) {
-          var policy = reqOpts.json.autoscalingPolicy;
+          let policy = reqOpts.json.autoscalingPolicy;
           assert.strictEqual(policy.maxNumReplicas, config.maxReplicas);
           assert.strictEqual(reqOpts.maxReplicas, undefined);
           done();
@@ -379,13 +379,13 @@ describe('Zone', function() {
 
     describe('config.minReplicas', function() {
       it('should set minNumReplicas', function(done) {
-        var config = {
+        let config = {
           minReplicas: 10,
           target: TARGET,
         };
 
         zone.request = function(reqOpts) {
-          var policy = reqOpts.json.autoscalingPolicy;
+          let policy = reqOpts.json.autoscalingPolicy;
           assert.strictEqual(policy.minNumReplicas, config.minReplicas);
           assert.strictEqual(reqOpts.minReplicas, undefined);
           done();
@@ -396,13 +396,13 @@ describe('Zone', function() {
     });
 
     describe('API request', function() {
-      var CONFIG = {
+      let CONFIG = {
         a: 'b',
         c: 'd',
         target: 'http://target',
       };
 
-      var expectedBody = {
+      let expectedBody = {
         name: NAME,
         target: 'http://target',
         autoscalingPolicy: {},
@@ -423,8 +423,8 @@ describe('Zone', function() {
       });
 
       describe('error', function() {
-        var error = new Error('Error.');
-        var apiResponse = {a: 'b', c: 'd'};
+        let error = new Error('Error.');
+        let apiResponse = {a: 'b', c: 'd'};
 
         beforeEach(function() {
           zone.request = function(reqOpts, callback) {
@@ -444,7 +444,7 @@ describe('Zone', function() {
       });
 
       describe('success', function() {
-        var apiResponse = {name: 'operation-name'};
+        let apiResponse = {name: 'operation-name'};
 
         beforeEach(function() {
           zone.request = function(reqOpts, callback) {
@@ -453,8 +453,8 @@ describe('Zone', function() {
         });
 
         it('should exec callback with AutoS, Op & apiResponse', function(done) {
-          var autoscaler = {};
-          var operation = {};
+          let autoscaler = {};
+          let operation = {};
 
           zone.autoscaler = function(name) {
             assert.strictEqual(name, NAME);
@@ -483,14 +483,14 @@ describe('Zone', function() {
   });
 
   describe('createDisk', function() {
-    var NAME = 'disk-name';
+    let NAME = 'disk-name';
 
     beforeEach(function() {
       zone.request = util.noop;
     });
 
     it('should use the image property as qs.sourceImages', function(done) {
-      var config = {
+      let config = {
         image: 'abc',
       };
 
@@ -503,7 +503,7 @@ describe('Zone', function() {
     });
 
     describe('config.os', function() {
-      var CONFIG = {
+      let CONFIG = {
         os: 'os-name',
       };
 
@@ -517,7 +517,7 @@ describe('Zone', function() {
       });
 
       describe('error', function() {
-        var error = new Error('Error.');
+        let error = new Error('Error.');
 
         beforeEach(function() {
           zone.gceImages.getLatest = function(os, callback) {
@@ -534,11 +534,11 @@ describe('Zone', function() {
       });
 
       describe('success', function() {
-        var gceImagesResp = {
+        let gceImagesResp = {
           selfLink: 'http://selflink',
         };
 
-        var expectedConfig = {
+        let expectedConfig = {
           name: NAME,
           sourceImage: gceImagesResp.selfLink,
         };
@@ -560,12 +560,12 @@ describe('Zone', function() {
     });
 
     describe('API request', function() {
-      var CONFIG = {
+      let CONFIG = {
         a: 'b',
         c: 'd',
       };
 
-      var expectedBody = {
+      let expectedBody = {
         name: NAME,
         a: 'b',
         c: 'd',
@@ -585,8 +585,8 @@ describe('Zone', function() {
       });
 
       describe('error', function() {
-        var error = new Error('Error.');
-        var apiResponse = {a: 'b', c: 'd'};
+        let error = new Error('Error.');
+        let apiResponse = {a: 'b', c: 'd'};
 
         beforeEach(function() {
           zone.request = function(reqOpts, callback) {
@@ -606,7 +606,7 @@ describe('Zone', function() {
       });
 
       describe('success', function() {
-        var apiResponse = {name: 'operation-name'};
+        let apiResponse = {name: 'operation-name'};
 
         beforeEach(function() {
           zone.request = function(reqOpts, callback) {
@@ -615,8 +615,8 @@ describe('Zone', function() {
         });
 
         it('should exec callback with Disk, Op & apiResponse', function(done) {
-          var disk = {};
-          var operation = {};
+          let disk = {};
+          let operation = {};
 
           zone.disk = function(name) {
             assert.strictEqual(name, NAME);
@@ -645,20 +645,20 @@ describe('Zone', function() {
   });
 
   describe('createInstanceGroup', function() {
-    var NAME = 'instance-group';
+    let NAME = 'instance-group';
 
     beforeEach(function() {
       zone.request = util.noop;
     });
 
     describe('options.ports', function() {
-      var PORTS = {
+      let PORTS = {
         http: 80,
         https: 443,
       };
 
       it('should format named ports', function(done) {
-        var expectedNamedPorts = [];
+        let expectedNamedPorts = [];
 
         formatPortsOverride = function(ports) {
           assert.strictEqual(ports, PORTS);
@@ -676,12 +676,12 @@ describe('Zone', function() {
     });
 
     describe('API request', function() {
-      var OPTIONS = {
+      let OPTIONS = {
         a: 'b',
         c: 'd',
       };
 
-      var expectedBody = {
+      let expectedBody = {
         name: NAME,
         a: 'b',
         c: 'd',
@@ -709,8 +709,8 @@ describe('Zone', function() {
       });
 
       describe('error', function() {
-        var error = new Error('Error.');
-        var apiResponse = {a: 'b', c: 'd'};
+        let error = new Error('Error.');
+        let apiResponse = {a: 'b', c: 'd'};
 
         beforeEach(function() {
           zone.request = function(reqOpts, callback) {
@@ -730,7 +730,7 @@ describe('Zone', function() {
       });
 
       describe('success', function() {
-        var apiResponse = {name: 'operation-name'};
+        let apiResponse = {name: 'operation-name'};
 
         beforeEach(function() {
           zone.request = function(reqOpts, callback) {
@@ -739,8 +739,8 @@ describe('Zone', function() {
         });
 
         it('should exec callback with Group, Op & apiResponse', function(done) {
-          var instanceGroup = {};
-          var operation = {};
+          let instanceGroup = {};
+          let operation = {};
 
           zone.instanceGroup = function(name) {
             assert.strictEqual(name, NAME);
@@ -769,11 +769,11 @@ describe('Zone', function() {
   });
 
   describe('createVM', function() {
-    var NAME = 'new-vm';
+    let NAME = 'new-vm';
 
-    var CONFIG = {};
+    let CONFIG = {};
 
-    var EXPECTED_CONFIG = {
+    let EXPECTED_CONFIG = {
       name: NAME,
       machineType: 'zones/' + ZONE_NAME + '/machineTypes/n1-standard-1',
       networkInterfaces: [
@@ -784,7 +784,7 @@ describe('Zone', function() {
     };
 
     describe('config.machineType', function() {
-      var CONFIG = {
+      let CONFIG = {
         machineType: 'f1-micro',
       };
 
@@ -802,7 +802,7 @@ describe('Zone', function() {
     });
 
     describe('config.tags', function() {
-      var CONFIG = {
+      let CONFIG = {
         tags: ['a', 'b'],
       };
 
@@ -817,7 +817,7 @@ describe('Zone', function() {
     });
 
     describe('config.http', function() {
-      var CONFIG = {
+      let CONFIG = {
         http: true,
       };
 
@@ -828,7 +828,7 @@ describe('Zone', function() {
       });
 
       it('should execute cb with error from creating firewall', function(done) {
-        var error = new Error('Error.');
+        let error = new Error('Error.');
 
         zone.createHttpServerFirewall_ = function(callback) {
           callback(error);
@@ -872,14 +872,14 @@ describe('Zone', function() {
       });
 
       it('should not overwrite existing tags', function(done) {
-        var config = {
+        let config = {
           http: true,
           tags: {
             items: ['a', 'b'],
           },
         };
 
-        var expectedTags = ['a', 'b', 'http-server'];
+        let expectedTags = ['a', 'b', 'http-server'];
 
         zone.request = function(reqOpts) {
           assert.deepStrictEqual(reqOpts.json.tags.items, expectedTags);
@@ -900,7 +900,7 @@ describe('Zone', function() {
     });
 
     describe('config.https', function() {
-      var CONFIG = {
+      let CONFIG = {
         https: true,
       };
 
@@ -911,7 +911,7 @@ describe('Zone', function() {
       });
 
       it('should execute cb with error from creating firewall', function(done) {
-        var error = new Error('Error.');
+        let error = new Error('Error.');
 
         zone.createHttpsServerFirewall_ = function(callback) {
           callback(error);
@@ -955,14 +955,14 @@ describe('Zone', function() {
       });
 
       it('should not overwrite existing tags', function(done) {
-        var config = {
+        let config = {
           https: true,
           tags: {
             items: ['a', 'b'],
           },
         };
 
-        var expectedTags = ['a', 'b', 'https-server'];
+        let expectedTags = ['a', 'b', 'https-server'];
 
         zone.request = function(reqOpts) {
           assert.deepStrictEqual(reqOpts.json.tags.items, expectedTags);
@@ -983,7 +983,7 @@ describe('Zone', function() {
     });
 
     describe('config.os', function() {
-      var CONFIG = {
+      let CONFIG = {
         os: 'os-name',
       };
 
@@ -997,7 +997,7 @@ describe('Zone', function() {
       });
 
       describe('error', function() {
-        var error = new Error('Error.');
+        let error = new Error('Error.');
 
         beforeEach(function() {
           zone.gceImages.getLatest = function(os, callback) {
@@ -1014,11 +1014,11 @@ describe('Zone', function() {
       });
 
       describe('success', function() {
-        var gceImagesResp = {
+        let gceImagesResp = {
           selfLink: 'http://selflink',
         };
 
-        var expectedConfig = extend({}, EXPECTED_CONFIG, {
+        let expectedConfig = extend({}, EXPECTED_CONFIG, {
           disks: [
             {
               autoDelete: true,
@@ -1060,8 +1060,8 @@ describe('Zone', function() {
       });
 
       describe('error', function() {
-        var error = new Error('Error.');
-        var apiResponse = {a: 'b', c: 'd'};
+        let error = new Error('Error.');
+        let apiResponse = {a: 'b', c: 'd'};
 
         beforeEach(function() {
           zone.request = function(reqOpts, callback) {
@@ -1081,7 +1081,7 @@ describe('Zone', function() {
       });
 
       describe('success', function() {
-        var apiResponse = {name: 'operation-name'};
+        let apiResponse = {name: 'operation-name'};
 
         beforeEach(function() {
           zone.request = function(reqOpts, callback) {
@@ -1090,8 +1090,8 @@ describe('Zone', function() {
         });
 
         it('should exec callback with Disk, Op & apiResponse', function(done) {
-          var vm = {};
-          var operation = {};
+          let vm = {};
+          let operation = {};
 
           zone.vm = function(name) {
             assert.strictEqual(name, NAME);
@@ -1120,10 +1120,10 @@ describe('Zone', function() {
   });
 
   describe('disk', function() {
-    var NAME = 'disk-name';
+    let NAME = 'disk-name';
 
     it('should return a Disk object', function() {
-      var disk = zone.disk(NAME);
+      let disk = zone.disk(NAME);
       assert(disk instanceof FakeDisk);
       assert.strictEqual(disk.calledWith_[0], zone);
       assert.strictEqual(disk.calledWith_[1], NAME);
@@ -1141,7 +1141,7 @@ describe('Zone', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/autoscalers');
@@ -1154,8 +1154,8 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         zone.request = function(reqOpts, callback) {
@@ -1175,7 +1175,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{name: 'autoscaler-name'}],
       };
 
@@ -1186,11 +1186,11 @@ describe('Zone', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -1208,7 +1208,7 @@ describe('Zone', function() {
       });
 
       it('should execute callback with Autoscalers & API resp', function(done) {
-        var autoscaler = {};
+        let autoscaler = {};
 
         zone.autoscaler = function(name) {
           assert.strictEqual(name, apiResponse.items[0].name);
@@ -1240,7 +1240,7 @@ describe('Zone', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/disks');
@@ -1253,8 +1253,8 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         zone.request = function(reqOpts, callback) {
@@ -1274,7 +1274,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{name: 'disk-name'}],
       };
 
@@ -1285,11 +1285,11 @@ describe('Zone', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -1307,7 +1307,7 @@ describe('Zone', function() {
       });
 
       it('should execute callback with Disks & API resp', function(done) {
-        var disk = {};
+        let disk = {};
 
         zone.disk = function(name) {
           assert.strictEqual(name, apiResponse.items[0].name);
@@ -1339,7 +1339,7 @@ describe('Zone', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/instanceGroups');
@@ -1352,8 +1352,8 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         zone.request = function(reqOpts, callback) {
@@ -1373,7 +1373,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{name: 'operation-name'}],
       };
 
@@ -1384,11 +1384,11 @@ describe('Zone', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -1406,7 +1406,7 @@ describe('Zone', function() {
       });
 
       it('should execute callback with Groups & API resp', function(done) {
-        var group = {};
+        let group = {};
 
         zone.instanceGroup = function(name) {
           assert.strictEqual(name, apiResponse.items[0].name);
@@ -1429,8 +1429,8 @@ describe('Zone', function() {
 
   describe('getMachineTypes', function() {
     it('should make the correct call to Compute', function(done) {
-      var options = {a: 'b', c: 'd'};
-      var expectedOptions = extend({}, options, {
+      let options = {a: 'b', c: 'd'};
+      let expectedOptions = extend({}, options, {
         filter: 'zone eq .*' + zone.name,
       });
 
@@ -1463,7 +1463,7 @@ describe('Zone', function() {
     });
 
     it('should return the result of compute.getMachineTypes', function() {
-      var resultOfGetMachineTypes = {};
+      let resultOfGetMachineTypes = {};
 
       zone.compute.getMachineTypes = function() {
         return resultOfGetMachineTypes;
@@ -1484,7 +1484,7 @@ describe('Zone', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/operations');
@@ -1497,8 +1497,8 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         zone.request = function(reqOpts, callback) {
@@ -1517,7 +1517,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{name: 'operation-name'}],
       };
 
@@ -1528,11 +1528,11 @@ describe('Zone', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -1550,7 +1550,7 @@ describe('Zone', function() {
       });
 
       it('should execute callback with Operations & API resp', function(done) {
-        var operation = {};
+        let operation = {};
 
         zone.operation = function(name) {
           assert.strictEqual(name, apiResponse.items[0].name);
@@ -1582,7 +1582,7 @@ describe('Zone', function() {
     });
 
     it('should make the correct API request', function(done) {
-      var query = {a: 'b', c: 'd'};
+      let query = {a: 'b', c: 'd'};
 
       zone.request = function(reqOpts) {
         assert.strictEqual(reqOpts.uri, '/instances');
@@ -1595,8 +1595,8 @@ describe('Zone', function() {
     });
 
     describe('error', function() {
-      var error = new Error('Error.');
-      var apiResponse = {a: 'b', c: 'd'};
+      let error = new Error('Error.');
+      let apiResponse = {a: 'b', c: 'd'};
 
       beforeEach(function() {
         zone.request = function(reqOpts, callback) {
@@ -1615,7 +1615,7 @@ describe('Zone', function() {
     });
 
     describe('success', function() {
-      var apiResponse = {
+      let apiResponse = {
         items: [{name: 'vm-name'}],
       };
 
@@ -1626,11 +1626,11 @@ describe('Zone', function() {
       });
 
       it('should build a nextQuery if necessary', function(done) {
-        var nextPageToken = 'next-page-token';
-        var apiResponseWithNextPageToken = extend({}, apiResponse, {
+        let nextPageToken = 'next-page-token';
+        let apiResponseWithNextPageToken = extend({}, apiResponse, {
           nextPageToken: nextPageToken,
         });
-        var expectedNextQuery = {
+        let expectedNextQuery = {
           pageToken: nextPageToken,
         };
 
@@ -1648,7 +1648,7 @@ describe('Zone', function() {
       });
 
       it('should execute callback with VMs & API response', function(done) {
-        var vm = {};
+        let vm = {};
 
         zone.vm = function(name) {
           assert.strictEqual(name, apiResponse.items[0].name);
@@ -1670,10 +1670,10 @@ describe('Zone', function() {
   });
 
   describe('instanceGroup', function() {
-    var NAME = 'instance-group';
+    let NAME = 'instance-group';
 
     it('should return an InstanceGroup object', function() {
-      var instanceGroup = zone.instanceGroup(NAME);
+      let instanceGroup = zone.instanceGroup(NAME);
       assert(instanceGroup instanceof FakeInstanceGroup);
       assert.strictEqual(instanceGroup.calledWith_[0], zone);
       assert.strictEqual(instanceGroup.calledWith_[1], NAME);
@@ -1681,10 +1681,10 @@ describe('Zone', function() {
   });
 
   describe('machineType', function() {
-    var NAME = 'machine-name';
+    let NAME = 'machine-name';
 
     it('should return a MachineType object', function() {
-      var machineType = zone.machineType(NAME);
+      let machineType = zone.machineType(NAME);
 
       assert(machineType instanceof FakeMachineType);
       assert.strictEqual(machineType.calledWith_[0], zone);
@@ -1693,10 +1693,10 @@ describe('Zone', function() {
   });
 
   describe('operation', function() {
-    var NAME = 'operation-name';
+    let NAME = 'operation-name';
 
     it('should return an Operation object', function() {
-      var operation = zone.operation(NAME);
+      let operation = zone.operation(NAME);
       assert(operation instanceof FakeOperation);
       assert.strictEqual(operation.calledWith_[0], zone);
       assert.strictEqual(operation.calledWith_[1], NAME);
@@ -1704,10 +1704,10 @@ describe('Zone', function() {
   });
 
   describe('vm', function() {
-    var NAME = 'vm-name';
+    let NAME = 'vm-name';
 
     it('should return a VM object', function() {
-      var vm = zone.vm(NAME);
+      let vm = zone.vm(NAME);
       assert(vm instanceof FakeVM);
       assert.strictEqual(vm.calledWith_[0], zone);
       assert.strictEqual(vm.calledWith_[1], NAME);
@@ -1733,7 +1733,7 @@ describe('Zone', function() {
     });
 
     it('should execute callback with error & API response', function(done) {
-      var error = new Error('Error.');
+      let error = new Error('Error.');
 
       zone.compute.createFirewall = function(name, config, callback) {
         callback(error);
@@ -1746,10 +1746,10 @@ describe('Zone', function() {
     });
 
     it('should not execute callback with error if 409', function(done) {
-      var error = new Error('Error.');
+      let error = new Error('Error.');
       error.code = 409;
 
-      var apiResponse = {};
+      let apiResponse = {};
 
       zone.compute.createFirewall = function(name, config, callback) {
         callback(error, null, apiResponse);
@@ -1781,7 +1781,7 @@ describe('Zone', function() {
     });
 
     it('should execute callback with error & API response', function(done) {
-      var error = new Error('Error.');
+      let error = new Error('Error.');
 
       zone.compute.createFirewall = function(name, config, callback) {
         callback(error);
@@ -1794,7 +1794,7 @@ describe('Zone', function() {
     });
 
     it('should not execute callback with error if 409', function(done) {
-      var error = new Error('Error.');
+      let error = new Error('Error.');
       error.code = 409;
 
       zone.compute.createFirewall = function(name, config, callback) {