feat(sharedBehavior): adds possibility to pass function in

`includeExamplesFor` and `itBehavesLike`

interface.d.ts

@@ -2,8 +2,10 @@ interface GetLazyVar {
   (name: string): any;
 }
 
+type AnyFunction = (...args: any[]) => any;
+
 export const get: GetLazyVar;
 export function def(name: string, implementation: () => any): void;
 export function sharedExamplesFor(summary: string, implementation: (...vars: any[]) => void): void;
-export function itBehavesLike(summary: string, ...vars: any[]): void;
-export function includeExamplesFor(summary: string, ...vars: any[]): void;
+export function itBehavesLike(summary: string | AnyFunction, ...vars: any[]): void;
+export function includeExamplesFor(summary: string | AnyFunction, ...vars: any[]): void;

lib/interface.js

@@ -1,6 +1,6 @@
 const { Metadata } = require('./metadata');
 const Variable = require('./variable');
-const parseMessage = require('./parse_message');
+const { parseMessage, humanize } = require('./parse_message');
 
 module.exports = (context, tracker, options) => {
   const get = (varName) => Variable.evaluate(varName, { in: tracker.currentContext });
@@ -46,14 +46,21 @@ module.exports = (context, tracker, options) => {
   }
 
   function includeExamplesFor(name, ...args) {
-    Metadata.ensureDefinedOn(tracker.currentlyDefinedSuite)
-      .runExamplesFor(name, args);
+    const meta = Metadata.ensureDefinedOn(tracker.currentlyDefinedSuite);
+
+    if (typeof name === 'function') {
+      name(...args);
+    } else {
+      meta.runExamplesFor(name, args);
+    }
   }
 
-  function itBehavesLike(name, ...args) {
-    context.describe(`behaves like ${name}`, () => {
-      args.unshift(name);
-      includeExamplesFor.apply(tracker.currentlyDefinedSuite, args);
+  function itBehavesLike(...args) {
+    const nameOrFn = args[0];
+    const title = typeof nameOrFn === 'string' ? nameOrFn : humanize(fn.name || 'this');
+
+    context.describe(`behaves like ${title}`, () => {
+      includeExamplesFor(...args);
     });
   }
 

lib/parse_message.js

@@ -1,16 +1,31 @@
-module.exports = function parseMessage(fn) {
+function parseMessage(fn) {
   const matches = fn.toString().match(/is\.expected\.(\s+(?=\.)|.)+/g);
 
   if (!matches) {
     return '';
   }
 
   const prefixLength = 'is.expected.'.length;
-  const body = matches.reduce((message, chunk) => message.concat(chunk.trim()
-    .slice(prefixLength)
-    .replace(/[\s.]+/g, ' ')
-    .replace(/([a-z])([A-Z])/g, (_, before, letter) => `${before} ${letter.toLowerCase()}`)
-    .replace(/ and /g, ', ')), []);
+  const body = matches.reduce((message, chunk) => {
+    const cleanChunk = chunk.trim()
+      .slice(prefixLength)
+      .replace(/[\s.]+/g, ' ');
+    const humanized = humanize(cleanChunk).replace(/ and /g, ', ');
+    message.push(humanized);
+    return message;
+  }, []);
 
   return `is expected ${body.join(', ')}`;
 };
+
+function humanize(value) {
+  return value.replace(
+    /([a-z])([A-Z])/g,
+    (_, before, letter) => `${before} ${letter.toLowerCase()}`
+  );
+}
+
+module.exports = {
+  parseMessage,
+  humanize,
+};

spec/shared_behavior_spec.js

@@ -19,6 +19,7 @@ describe('Shared behavior', function() {
     var includeError;
     var examples = spy();
     var args = [{}, {}];
+    var fnDefinition = spy();
 
     try {
       includeExamplesFor('__non_existing')
@@ -28,6 +29,7 @@ describe('Shared behavior', function() {
 
     sharedExamplesFor('__call', examples);
     includeExamplesFor('__call', args[0], args[1]);
+    includeExamplesFor(fnDefinition, args[0]);
 
     it('throws error when trying to include non-existing shared examples', function() {
       expect(includeError.message).to.match(/not defined shared behavior/)
@@ -36,21 +38,32 @@ describe('Shared behavior', function() {
     it('calls registered shared examples with specified arguments', function() {
       expect(examples).to.have.been.called.with.exactly(args[0], args[1]);
     });
+
+    it('accepts function as the 1st argument and call it', () => {
+      expect(fnDefinition).to.have.been.called.with.exactly(args[0]);
+    })
   });
 
   describe('`itBehavesLike`', function() {
     var examples = spy();
     var args = [{}, {}];
     var spiedDescribe = spy.on(global, 'describe');
+    var fnBehavior = spy();
 
     sharedExamplesFor('__Collection', examples);
     itBehavesLike('__Collection', args[0], args[1]);
     spy.restore(global, 'describe');
 
+    itBehavesLike(fnBehavior, args[0]);
+
     it('includes examples in a nested context', function() {
       expect(spiedDescribe).to.have.been.called.with('behaves like __Collection');
       expect(examples).to.have.been.called.with.exactly(args[0], args[1]);
     });
+
+    it('accepts behavior defined in function', function () {
+      expect(fnBehavior).to.have.been.called.with(args[0]);
+    });
   });
 
   describe('`sharedExamplesFor` scoping', function() {