public static ExecutorService getSingleThreadExecutor() {
        setup();
        return singleThreadExecutor;
    }
@Test
    public void singleThread() {
       ExecutorService a =  SharedExecutors.getSingleThreadExecutor();
       assertNotNull("ExecutorService must not be null", a);
       ExecutorService b =  SharedExecutors.getSingleThreadExecutor();
       assertSame("factories should be same", a, b);

    }