//    - getWaitingThreads(Guard) method
  //    - implement Serializable
  //    - redo the API to be as close to identical to ReentrantLock as possible,
  //      since, after all, this class is also a reentrant mutual exclusion lock!?

  /*
   * One of the key challenges of this class is to prevent lost signals, while trying hard to
   * minimize unnecessary signals. One simple and correct algorithm is to signal some other waiter

  @BeforeExperiment
  void setUp() throws Exception {
    if (state != State.NOT_DONE && (numListeners != 0 || numThreads != 0)) {
      throw new SkipThisScenarioException();
    }
  }

  // This exclusion doesn't exclude the TOMBSTONE objects we set. So 'done' NEW futures will look
  // larger than they are.
  @SuppressWarnings("FutureReturnValueIgnored")

  @BeforeExperiment
  void setUp() throws Exception {
    if (state != State.NOT_DONE && (numListeners != 0 || numThreads != 0)) {
      throw new SkipThisScenarioException();
    }
  }

  // This exclusion doesn't exclude the TOMBSTONE objects we set. So 'done' NEW futures will look
  // larger than they are.
  @SuppressWarnings("FutureReturnValueIgnored")