@Override
    public ScheduledFuture<?> schedule(Runnable command, long delay, TimeUnit unit) {
        return internalExecutor.schedule(command, delay, unit);
    }
@Test
    public void testSchedule() throws Exception {
        TestRunnable runnable = new TestRunnable();

        ScheduledFuture<?> future = executionService.schedule(runnable, 0, SECONDS);
        Object result = future.get();

        assertTrue(runnable.isExecuted());
        assertNull(result);
    }