anchor.diff:      return '';
     }
   
  -  shouldCallBack() {
  +  bool shouldCallBack() {
       ++actualCalls;
       if (testCase.isComplete) {
         // Don't run if the test is done. We don't throw here as this is not
  
positive.code: // TODO(sigmund): deprecate this API when issue 2706 is fixed.
  Function expectAsyncUntil2(Function callback, Function isDone, {String id}) {
    return new _SpreadArgsHelper(callback, 0, -1, isDone, id).invoke2;
  }
  
  /**
   * Wraps the [callback] in a new function and returns that function. The new
   * function will be able to handle exceptions by directing them to the correct
   * test. This is thus similar to expectAsync0. Use it to wrap any callbacks that
   * might optionally be called but may never be called during the test.
   * [callback] should take between 0 and 4 positional arguments (named arguments
   * are not supported). [id] can be used to identify the callback in error
   * messages (for example if it is called after the test case is complete).
   */
  Function _protectAsync(Function callback, {String id}) {
    return new _SpreadArgsHelper(callback, 0, -1, null, id).invoke;
  }
  
  /**
  
negative.code:       complete = true;
        testCase._markCallbackComplete();
      }
    }
  
    invoke0() {
  