test(core): Wait for zone stability before test completion

Need to wait for microtaskEmty to emit or test will leak into others.

packages/core/test/zone/ng_zone_spec.ts

@@ -9,6 +9,7 @@
 import {EventEmitter, NgZone} from '@angular/core';
 import {fakeAsync, flushMicrotasks, inject, waitForAsync} from '@angular/core/testing';
 import {Log} from '@angular/core/testing/src/testing_internal';
+import {firstValueFrom} from 'rxjs';
 
 import {scheduleCallbackWithRafRace as scheduler} from '../../src/util/callback_scheduler';
 import {global} from '../../src/util/global';
@@ -1193,10 +1194,11 @@ function commonTests() {
            });
          });
 
-      it('does not throw when apply args array has `undefined`', () => {
+      it('does not throw when apply args array has `undefined`', async () => {
         expect(() => {
           coalesceZone.run(function(this: any, arg: any) {}, undefined, [undefined]);
         }).not.toThrow();
+        await firstValueFrom(coalesceZone.onMicrotaskEmpty);
       });
     });
   });