anchor.diff:        _uncaughtError = true;
       } else if (_callbacksCalled == testCase.callbacks) {
         testCase.recordSuccess();
  -      _currentTest++;
  -      _nextBatch();
  +      if (!_testIsRunning) {
  +        _currentTest++;
  +        _nextBatch();
  +      }
       }
     }
   
  
positive.code:     _uncaughtError = false;
      _callbacksCalled = 0;
      try {
        (testCase.test)();
        if (!_uncaughtError) {
          if (testCase.callbacks == _callbacksCalled) {
  
negative.code:   EventListener _onErrorClosure;
  
    bool _queuedToRun = false;
  
    /** Whether a test is currently being executed by [runTest]. */
    bool _testIsRunning = false;
  
    // TODO(sigmund): remove isLayoutTest argument after converting all DOM tests
    // to use the named constructor below.
  