feat(spec): add an option to FakeAsyncTestZoneSpec to flush periodic timers (#857)

A flush with flushPeriodic set to true will flush till all the pending
timers in the queue have been visited atleast once.

Author: vikerman

Diff for: lib/zone-spec/fake-async-test.ts

@@ -91,22 +91,39 @@
       this._currentTime = finalTime;
     }
 
-    flush(limit: number = 20): number {
+    flush(limit: number = 20, flushPeriodic = false): number {
       const startTime = this._currentTime;
       let count = 0;
+      let seenTimers: number[] = [];
       while (this._schedulerQueue.length > 0) {
         count++;
         if (count > limit) {
           throw new Error(
               'flush failed after reaching the limit of ' + limit +
               ' tasks. Does your code use a polling timeout?');
         }
-        // If the only remaining tasks are periodic, finish flushing.
-        if (!(this._schedulerQueue.filter(task => !task.isPeriodic && !task.isRequestAnimationFrame)
-                  .length)) {
-          break;
+        if (!flushPeriodic) {
+          // flush only non-periodic timers.
+          // If the only remaining tasks are periodic(or requestAnimationFrame), finish flushing.
+          if (this._schedulerQueue.filter(task => !task.isPeriodic && !task.isRequestAnimationFrame)
+                  .length === 0) {
+            break;
+          }
+        } else {
+          // flushPeriodic has been requested.
+          // Stop when all timer id-s have been seen at least once.
+          if (this._schedulerQueue
+                  .filter(
+                      task =>
+                          seenTimers.indexOf(task.id) === -1 || this._currentTime === task.endTime)
+                  .length === 0) {
+            break;
+          }
         }
         let current = this._schedulerQueue.shift();
+        if (seenTimers.indexOf(current.id) === -1) {
+          seenTimers.push(current.id);
+        }
         this._currentTime = current.endTime;
         let retval = current.func.apply(global, current.args);
         if (!retval) {
@@ -254,10 +271,10 @@
       flushErrors();
     }
 
-    flush(limit?: number): number {
+    flush(limit?: number, flushPeriodic?: boolean): number {
       FakeAsyncTestZoneSpec.assertInZone();
       this.flushMicrotasks();
-      let elapsed = this._scheduler.flush(limit);
+      let elapsed = this._scheduler.flush(limit, flushPeriodic);
       if (this._lastError !== null) {
         this._resetLastErrorAndThrow();
       }

Diff for: test/zone-spec/fake-async-test.spec.ts

@@ -502,7 +502,7 @@ describe('FakeAsyncTestZoneSpec', () => {
               'flush failed after reaching the limit of 20 tasks. Does your code use a polling timeout?');
     });
 
-    it('accepts a custom limit', function() {
+    it('accepts a custom limit', () => {
       expect(() => {
         fakeAsyncTestZone.run(() => {
           let z = 0;
@@ -521,6 +521,42 @@ describe('FakeAsyncTestZoneSpec', () => {
           .toThrowError(
               'flush failed after reaching the limit of 10 tasks. Does your code use a polling timeout?');
     });
+
+    it('can flush periodic timers if flushPeriodic is true', () => {
+      fakeAsyncTestZone.run(() => {
+        let x = 0;
+
+        setInterval(() => {
+          x++;
+        }, 10);
+
+        let elapsed = testZoneSpec.flush(20, true);
+
+        expect(elapsed).toEqual(10);
+        expect(x).toEqual(1);
+      });
+    });
+
+    it('can flush multiple periodic timers if flushPeriodic is true', () => {
+      fakeAsyncTestZone.run(() => {
+        let x = 0;
+        let y = 0;
+
+        setInterval(() => {
+          x++;
+        }, 10);
+
+        setInterval(() => {
+          y++;
+        }, 100);
+
+        let elapsed = testZoneSpec.flush(20, true);
+
+        expect(elapsed).toEqual(100);
+        expect(x).toEqual(10);
+        expect(y).toEqual(1);
+      });
+    });
   });
 
   describe('outside of FakeAsync Zone', () => {
@@ -578,6 +614,27 @@ describe('FakeAsyncTestZoneSpec', () => {
                      expect(ran).toEqual(false);
                    });
                  });
+                 it('is not flushed when flushPeriodic is false', () => {
+                   let ran = false;
+                   fakeAsyncTestZone.run(() => {
+                     requestAnimationFrame(() => {
+                       ran = true;
+                     });
+                     testZoneSpec.flush(20);
+                     expect(ran).toEqual(false);
+                   });
+                 });
+                 it('is flushed when flushPeriodic is true', () => {
+                   let ran = false;
+                   fakeAsyncTestZone.run(() => {
+                     requestAnimationFrame(() => {
+                       ran = true;
+                     });
+                     const elapsed = testZoneSpec.flush(20, true);
+                     expect(elapsed).toEqual(16);
+                     expect(ran).toEqual(true);
+                   });
+                 });
                }));
     });
   });