anchor.diff:    final int minExpectedCalls;
     final int maxExpectedCalls;
     final Function isDone;
  -  final int testNum;
  +  final TestCase testCase;
     final String id;
     int actualCalls = 0;
  -  TestCase testCase;
     bool complete;
     static const sentinel = const _Sentinel();
   
  
positive.code:             return callback(arg1, arg2);
            }
          },
          after, testNum);
    }
  }
  
  /**
   * Indicate that [callback] is expected to be called a [count] number of times
   * (by default 1). The unittest framework will wait for the callback to run the
   * specified [count] times before it continues with the following test.  Using
   * [_expectAsync] will also ensure that errors that occur within [callback] are
   * tracked and reported. [callback] should take between 0 and 4 positional
   * arguments (named arguments are not supported here). [id] can be used
   * to provide more descriptive error messages if the callback is called more
   * often than expected.
   */
  Function _expectAsync(Function callback,
                       {int count: 1, int max: 0, String id}) {
    return new _SpreadArgsHelper(callback, count, max, null, id).invoke;
  }
  
  /**
  
negative.code: 
    _config.onStart();
  
    new Future(_nextBatch);
  }
  
  /**
  