anchor.diff:                if (tearDown != null) {
                   return tearDown();
                 }
  -            }).catchError(errorHandler('Teardown'));
  +            }).catchError(_errorHandler('Teardown'));
             } else if (tearDown != null) {
               return tearDown();
             }
           })
  -        .catchError(errorHandler('Teardown'));
  +        .catchError(_errorHandler('Teardown'));
     }
   
     // Set the results, notify the config, and return true if this
  
positive.code: 
    bool get isComplete => !enabled || result != null;
  
    errorHandler(stage) => (e) {
      var stack = getAttachedStackTrace(e);
      if (result == null || result == PASS) {
        if (e is TestFailure) {
  
negative.code:           ++_callbackFunctionsOutstanding;
            return testFunction();
          })
          .catchError(_errorHandler('Test'))
          .then((_) {
            _markCallbackComplete();
            if (result == null) {
  