// Set to null
        CrawlingParameterUtil.setDataService(null);

        // Should be null now
        assertNull(CrawlingParameterUtil.getDataService());
    }

    public void test_threadLocal_isolation() throws Exception {
        // Set values in main thread
        UrlQueue<?> mainUrlQueue = createMockUrlQueue("main-thread", "http://main.com");
        CrawlingParameterUtil.setUrlQueue(mainUrlQueue);