anchor.diff:    } else if (testFilter is Function) {
       filterFunction = testFilter;
     }
  -  _testCases.retainWhere(filterFunction);
  +  testCases.retainWhere(filterFunction);
   }
   
   /** Runs all queued tests, one at a time. */
  
positive.code: /** Enable/disable a test by ID. */
  void _setTestEnabledState(int testId, bool state) {
    // Try fast path first.
    if (_testCases.length > testId && _testCases[testId].id == testId) {
      _testCases[testId].enabled = state;
    } else {
      for (var i = 0; i < _testCases.length; i++) {
        if (_testCases[i].id == testId) {
          _testCases[i].enabled = state;
          break;
        }
      }
  
negative.code: 
  /** [TestCase] currently being executed. */
  TestCase get currentTestCase =>
      (_currentTestCaseIndex >= 0 && _currentTestCaseIndex < testCases.length)
          ? testCases[_currentTestCaseIndex]
          : null;
  
  /** Whether the framework is in an initialized state. */
  