@Override
  public <T> Future<T> submit(Callable<T> callable) {
    return schedule(callable, 0, TimeUnit.SECONDS);
  }
@Test
  public void submit() throws Exception {
    CountTask task = new CountTask();
    ControllableScheduler scheduler = new ControllableScheduler();
    scheduler.submit(task);
    assertFalse(scheduler.schedulerIsIdle());
    scheduler.runNextPendingCommand();
    assertEquals(1, task.runTimes());
    assertTrue(scheduler.schedulerIsIdle());
  }