anchor.diff:  
       future.onComplete(onComplete);
     }
  -
  -  static bool _goodTask(TaskContext context) {
  -    return true;
  -  }
  -
  -  static bool _failedTask(TaskContext context) {
  -    return false;
  -  }
  -
  -  static bool _sadTask(TaskContext context) {
  -    return null;
  -  }
   }
positive.code: 
    static void _testTrueIsCool() {
      final tasks = new Tasks();
      tasks.addTask('good', _goodTask);
      tasks.freeze();
  
      final runner = new Runner(tasks, ['good']);
  
negative.code: 
    static void _testFalseIsFail() {
      final tasks = new Tasks();
      tasks.addTask('fail', (ctx) => false);
      tasks.freeze();
  
      final runner = new Runner(tasks, ['fail']);
  