feat($httpBackend): flush requests in desired order

It was impossible to flush pending requests in desired order.
Now it is possible because you can specify a `start` number.

Author: dizel3d

src/ngMock/angular-mocks.js

@@ -1788,24 +1788,29 @@ function createHttpBackendMock($rootScope, $timeout, $delegate, $browser) {
    * @ngdoc method
    * @name $httpBackend#flush
    * @description
-   * Flushes all pending requests using the trained responses.
+   * Flushes pending requests using the trained responses in the order they arrived.
+   * If there are no pending requests when the flush method is called
+   * an exception is thrown (as this typically a sign of programming error).
    *
-   * @param {number=} count Number of responses to flush (in the order they arrived). If undefined,
-   *   all pending requests will be flushed. If there are no pending requests when the flush method
-   *   is called an exception is thrown (as this typically a sign of programming error).
+   * @param {number=} count Number of responses to flush. If undefined,
+   *   all pending requests will be flushed beginning at `start`.
+   * @param {number=} [start=0] Sequential request number at which to begin to flush.
    */
-  $httpBackend.flush = function(count, digest) {
+  $httpBackend.flush = function(count, start, digest) {
     if (digest !== false) $rootScope.$digest();
     if (!responses.length) throw new Error('No pending request to flush !');
 
+    start = angular.isDefined(start) && start !== null ? start : 0;
+
     if (angular.isDefined(count) && count !== null) {
       while (count--) {
-        if (!responses.length) throw new Error('No more pending request to flush !');
-        responses.shift()();
+        var part = responses.splice(start, 1);
+        if (!part.length) throw new Error('No more pending request to flush !');
+        part[0]();
       }
     } else {
-      while (responses.length) {
-        responses.shift()();
+      while (responses.length > start) {
+        responses.splice(start, 1)[0]();
       }
     }
     $httpBackend.verifyNoOutstandingExpectation(digest);

test/ng/httpSpec.js

@@ -2210,7 +2210,7 @@ describe('$http with $applyAsync', function() {
     // Ensure requests are sent
     $rootScope.$digest();
 
-    $httpBackend.flush(null, false);
+    $httpBackend.flush(null, null, false);
     expect($rootScope.$applyAsync).toHaveBeenCalledOnce();
     expect(handler).not.toHaveBeenCalled();
 
@@ -2228,7 +2228,7 @@ describe('$http with $applyAsync', function() {
     // Ensure requests are sent
     $rootScope.$digest();
 
-    $httpBackend.flush(null, false);
+    $httpBackend.flush(null, null, false);
     expect(log).toEqual([]);
 
     $browser.defer.flush();
@@ -2253,7 +2253,7 @@ describe('$http with $applyAsync', function() {
     expect(log).toEqual(['response 1', 'response 2']);
 
     // Finally, third response is received, and a second coalesced $apply is started
-    $httpBackend.flush(null, false);
+    $httpBackend.flush(null, null, false);
     $browser.defer.flush();
     expect(log).toEqual(['response 1', 'response 2', 'response 3']);
   });

test/ngMock/angular-mocksSpec.js

@@ -1532,6 +1532,38 @@ describe('ngMock', function() {
       });
 
 
+      it('should flush given number of pending requests beginning at specified request', function() {
+        var dontCallMe = jasmine.createSpy('dontCallMe');
+
+        hb.when('GET').respond(200, '');
+        hb('GET', '/some', null, dontCallMe);
+        hb('GET', '/some', null, callback);
+        hb('GET', '/some', null, callback);
+        hb('GET', '/some', null, dontCallMe);
+
+        hb.flush(2, 1);
+        expect(dontCallMe).not.toHaveBeenCalled();
+        expect(callback).toHaveBeenCalled();
+        expect(callback).toHaveBeenCalledTimes(2);
+      });
+
+
+      it('should flush all pending requests beginning at specified request', function() {
+        var dontCallMe = jasmine.createSpy('dontCallMe');
+
+        hb.when('GET').respond(200, '');
+        hb('GET', '/some', null, dontCallMe);
+        hb('GET', '/some', null, dontCallMe);
+        hb('GET', '/some', null, callback);
+        hb('GET', '/some', null, callback);
+
+        hb.flush(null, 2);
+        expect(dontCallMe).not.toHaveBeenCalled();
+        expect(callback).toHaveBeenCalled();
+        expect(callback).toHaveBeenCalledTimes(2);
+      });
+
+
       it('should throw exception when flushing more requests than pending', function() {
         hb.when('GET').respond(200, '');
         hb('GET', '/url', null, callback);