Added tests for DiscardEmptyTileImagePolicy, updated CHANGES.md

CHANGES.md

@@ -1,5 +1,9 @@
 Change Log
 ==========
+### 1.58 - 2019-06-01
+
+##### Additions :tada:
+* Added support for new Bing Maps imagery styles RoadOnDemand and AerialWithLabelsOnDemand. The other versions of these, Road and AerialWithLabels, have been deprecated. [#7808] (https://github.com/AnalyticalGraphicsInc/cesium/pull/7808)
 
 ### 1.57 - 2019-05-01
 

Source/Core/Resource.js

@@ -944,6 +944,7 @@ define([
                     window.URL.revokeObjectURL(generatedBlobResource.url);
                 }
 
+                // We attach additional information to the error here so that it can be handled by an ImageProvider.
                 error.blob = generatedBlob;
 
                 return when.reject(error);

Specs/Scene/DiscardEmptyTileImagePolicySpec.js

@@ -0,0 +1,54 @@
+defineSuite([
+        'Scene/DiscardEmptyTileImagePolicy',
+        'Core/Resource',
+        'Specs/pollToPromise',
+        'ThirdParty/when'
+    ], function(
+        DiscardEmptyTileImagePolicy,
+        Resource,
+        pollToPromise,
+        when) {
+    'use strict';
+
+    afterEach(function() {
+        Resource._Implementations.createImage = Resource._DefaultImplementations.createImage;
+        Resource._Implementations.loadWithXhr = Resource._DefaultImplementations.loadWithXhr;
+    });
+
+    describe('shouldDiscardImage', function() {
+        fit('does not discard a non-empty image', function() {
+            var promises = [];
+            promises.push(Resource.fetchImage('Data/Images/Green4x4.png'));
+
+            var policy = new DiscardEmptyTileImagePolicy();
+
+            promises.push(pollToPromise(function() {
+                return policy.isReady();
+            }));
+
+            return when.all(promises, function(results) {
+                var greenImage = results[0];
+
+                expect(policy.shouldDiscardImage(greenImage)).toEqual(false);
+            });
+        });
+
+        fit('discards an empty image', function() {
+            var promises = [];
+            promises.push(when.resolve(DiscardEmptyTileImagePolicy.EMPTY_IMAGE));
+
+            var policy = new DiscardEmptyTileImagePolicy();
+
+            promises.push(pollToPromise(function() {
+                return policy.isReady();
+            }));
+
+            return when.all(promises, function(results) {
+                var emptyImage = results[0];
+
+                expect(policy.shouldDiscardImage(emptyImage)).toEqual(true);
+            });
+        });
+
+    });
+});