feat(ngMock): $timeout.flushNext can expect specific timeout delays

the $timeout mock's flush method allows flushing queued up requests
but doesn't allow to for checking with what delay a task was queued
up. flushNext flushes the next queued up task and can asserts the
scheduled delay.

Author: matsko

src/ngMock/angular-mocks.js

@@ -118,6 +118,22 @@ angular.mock.$Browser = function() {
       self.deferredFns.shift().fn();
     }
   };
+
+  /**
+   * @name ngMock.$browser#defer.flushNext
+   * @methodOf ngMock.$browser
+   *
+   * @description
+   * Flushes next pending request and compares it to the provided delay
+   *
+   * @param {number=} expectedDelay the delay value that will be asserted against the delay of the next timeout function
+   */
+  self.defer.flushNext = function(expectedDelay) {
+    var tick = self.deferredFns.shift();
+    expect(tick.time).toEqual(expectedDelay);
+    tick.fn();
+  };
+
   /**
    * @name ngMock.$browser#defer.now
    * @propertyOf ngMock.$browser
@@ -1494,6 +1510,20 @@ angular.mock.$TimeoutDecorator = function($delegate, $browser) {
     $browser.defer.flush(delay);
   };
 
+  /**
+   * @ngdoc method
+   * @name ngMock.$timeout#flushNext
+   * @methodOf ngMock.$timeout
+   * @description
+   *
+   * Flushes the next timeout in the queue and compares it to the provided delay
+   *
+   * @param {number=} expectedDelay the delay value that will be asserted against the delay of the next timeout function
+   */
+  $delegate.flushNext = function(expectedDelay) {
+    $browser.defer.flushNext(expectedDelay);
+  };
+
   /**
    * @ngdoc method
    * @name ngMock.$timeout#verifyNoPendingTasks

test/ngMock/angular-mocksSpec.js

@@ -365,6 +365,21 @@ describe('ngMock', function() {
       $timeout.flush(900);
       expect(function() {$timeout.verifyNoPendingTasks();}).not.toThrow();
     }));
+
+
+    it('should assert against the delay value', inject(function($timeout) {
+      var count = 0;
+      var iterate = function() {
+        count++;
+      };
+
+      $timeout(iterate, 100);
+      $timeout(iterate, 123);
+      $timeout.flushNext(100);
+      expect(count).toBe(1);
+      $timeout.flushNext(123);
+      expect(count).toBe(2);
+    }));
   });