// get called correctly.
    for (int i = 0; i < 20; i++) {

      // Right in the middle start up a thread to close the latch.
      if (i == 10) {
        new Thread(() -> latch.countDown()).start();
      }

      future.addListener(listenerLatch::countDown, exec);
    }

    assertSame(Boolean.TRUE, future.get());

    // get called correctly.
    for (int i = 0; i < 20; i++) {

      // Right in the middle start up a thread to close the latch.
      if (i == 10) {
        new Thread(() -> latch.countDown()).start();
      }

      future.addListener(listenerLatch::countDown, exec);
    }

    assertSame(Boolean.TRUE, future.get());