anchor.diff:  
     bool get isComplete => !enabled || result != null;
   
  -  errorHandler(stage) => (e) {
  +  Function _errorHandler(String stage) => (e) {
       var stack = getAttachedStackTrace(e);
       if (result == null || result == PASS) {
         if (e is TestFailure) {
  
positive.code:               if (tearDown != null) {
                  return tearDown();
                }
              }).catchError(errorHandler('Teardown'));
            } else if (tearDown != null) {
              return tearDown();
            }
          })
          .catchError(errorHandler('Teardown'));
    }
  
    // Set the results, notify the config, and return true if this
  
negative.code:     _message = '';
  
      var f = (setUp == null) ? new Future.value() : new Future(setUp);
      return f.catchError(_errorHandler('Setup'))
          .then((_) {
            // Skip the test if setup failed.
            if (result != null) return new Future.value();
  