public static SharedScheduledExecutorService getPoolThreadExecutor() {
        setup();
        return poolThreadExecutor;
    }
@Test
    public void poolThread() {
        ScheduledExecutorService a = SharedScheduledExecutors.getPoolThreadExecutor();
        assertNotNull("ScheduledExecutorService must not be null", a);
        ScheduledExecutorService b = SharedScheduledExecutors.getPoolThreadExecutor();
        assertSame("factories should be same", a, b);
    }