anchor.diff:          ));
           assert(_parentZone != null);
           assert(_pendingExceptionDetails != null, 'A test overrode FlutterError.onError but either failed to return it to its original state, or had unexpected additional errors that it could not handle. Typically, this is caused by using expect() before restoring FlutterError.onError.');
  -        _parentZone.run<void>(_testCompletionHandler);
  +        _parentZone.run<void>(testCompletionHandler);
         }
       );
       _parentZone = Zone.current;
       final Zone testZone = _parentZone.fork(specification: errorHandlingZoneSpecification);
       testZone.runBinary(_runTestBody, testBody, invariantTester)
  -      .whenComplete(_testCompletionHandler);
  +      .whenComplete(testCompletionHandler);
       asyncBarrier(); // When using AutomatedTestWidgetsFlutterBinding, this flushes the microtasks.
  -    return _currentTestCompleter.future;
  +    return testCompleter.future;
     }
   
     Future<Null> _runTestBody(Future<Null> testBody(), VoidCallback invariantTester) async {
  
positive.code:   void _verifyInvariants() {
      super._verifyInvariants();
      assert(
        _fakeAsync.periodicTimerCount == 0,
        'A periodic Timer is still running even after the widget tree was disposed.'
      );
      assert(
        _fakeAsync.nonPeriodicTimerCount == 0,
        'A Timer is still pending even after the widget tree was disposed.'
      );
      assert(_fakeAsync.microtaskCount == 0); // Shouldn't be possible.
    }
  
    @override
    void postTest() {
      super.postTest();
      assert(_fakeAsync != null);
      assert(_clock != null);
      _clock = null;
      _fakeAsync = null;
    }
  
  }
  
negative.code:         _pendingExceptionDetails = details;
        }
      };
      final Completer<Null> testCompleter = new Completer<Null>();
      final VoidCallback testCompletionHandler = _createTestCompletionHandler(description, testCompleter);
      final ZoneSpecification errorHandlingZoneSpecification = new ZoneSpecification(
        handleUncaughtError: (Zone self, ZoneDelegate parent, Zone zone, dynamic exception, StackTrace stack) {
          if (testCompleter.isCompleted) {
            // Well this is not a good sign.
            // Ideally, once the test has failed we would stop getting errors from the test.
            // However, if someone tries hard enough they could get in a state where this happens.
  