String result4 = (String) method.invoke(crawler, dataMap, "key4", "default");
        assertEquals("default", result4);
    }

    // Test joinCrawlerThread private method via reflection
    public void test_joinCrawlerThread() throws Exception {
        Method method = Crawler.class.getDeclaredMethod("joinCrawlerThread", Thread.class);
        method.setAccessible(true);

        // Test with null thread
        try {