*     down the executor after the last event has been posted to this event bus.
   */
  public AsyncEventBus(String identifier, Executor executor) {
    super(identifier, executor, Dispatcher.legacyAsync(), LoggingHandler.INSTANCE);
  }

  /**
   * Creates a new AsyncEventBus that will use {@code executor} to dispatch events.
   *

   * For async dispatch, an {@linkplain #immediate() immediate} dispatcher should generally be
   * preferable.
   */
  static Dispatcher legacyAsync() {
    return new LegacyAsyncDispatcher();
  }

  /**
   * Returns a dispatcher that dispatches events to subscribers immediately as they're posted

            s1,
            s2 // subscribers have finished.
            )
        .inOrder();
  }

  public void testLegacyAsyncDispatcher() {
    dispatcher = Dispatcher.legacyAsync();

    final CyclicBarrier barrier = new CyclicBarrier(2);
    final CountDownLatch latch = new CountDownLatch(2);

    new Thread(
            new Runnable() {
              @Override

            s1,
            s2 // subscribers have finished.
            )
        .inOrder();
  }

  public void testLegacyAsyncDispatcher() {
    dispatcher = Dispatcher.legacyAsync();

    final CyclicBarrier barrier = new CyclicBarrier(2);
    final CountDownLatch latch = new CountDownLatch(2);

    new Thread(
            new Runnable() {
              @Override