@Override
                public Integer call() {
                  return counter.incrementAndGet();
                }
              });
      CyclicBarrier barrier = new CyclicBarrier(numThreads + 1);
      Runnable wrapper =
          new Runnable() {
            @Override
            public void run() {
              awaitUnchecked(barrier);
              task.run();

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

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

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

    new Thread(
            new Runnable() {
              @Override
              public void run() {
                try {