From e34eb4520f5db9e551f3520a2df3c6a9c7c571b9 Mon Sep 17 00:00:00 2001
From: vikerman <vikerman@users.noreply.github.com>
Date: Fri, 22 Jul 2016 16:07:11 -0700
Subject: [PATCH] fix(testing): ComponentFixture - Avoid extra
 scheduleMicrotask (#10223)

Don't schedule microtask to check for pending macrotasks when no one is waiting for a whenStable().
---
 .../core/testing/component_fixture.ts         | 22 +++++++++++--------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/modules/@angular/core/testing/component_fixture.ts b/modules/@angular/core/testing/component_fixture.ts
index cb7910e38e..4cb90592f8 100644
--- a/modules/@angular/core/testing/component_fixture.ts
+++ b/modules/@angular/core/testing/component_fixture.ts
@@ -87,16 +87,20 @@ export class ComponentFixture<T> {
           });
       this._onStableSubscription = ObservableWrapper.subscribe(ngZone.onStable, (_) => {
         this._isStable = true;
-        // Check whether there are no pending macrotasks in a microtask so that ngZone gets a chance
-        // to update the state of pending macrotasks.
-        scheduleMicroTask(() => {
-          if (!this.ngZone.hasPendingMacrotasks) {
-            if (this._completer != null) {
-              this._completer.resolve(true);
-              this._completer = null;
+        // Check whether there is a pending whenStable() completer to resolve.
+        if (this._completer !== null) {
+          // If so check whether there are no pending macrotasks before resolving.
+          // Do this check in the next tick so that ngZone gets a chance to update the state of
+          // pending macrotasks.
+          scheduleMicroTask(() => {
+            if (!this.ngZone.hasPendingMacrotasks) {
+              if (this._completer !== null) {
+                this._completer.resolve(true);
+                this._completer = null;
+              }
             }
-          }
-        });
+          });
+        }
       });
 
       this._onErrorSubscription = ObservableWrapper.subscribe(