}

    private void scheduleRelease(long countdownInMillis) {
      DelayedActionRunnable toRun = new Release(semaphore, countdownInMillis);
      // TODO(cpovirk): automatically fail the test if this thread throws
      Thread releaserThread = new Thread(toRun);
      releaserThread.start();
    }
  }

  private abstract static class DelayedActionRunnable implements Runnable {
    private final long tMinus;