newSet.add("http://new.com/robots.txt");
        crawlerContext.setRobotsTxtUrlSet(newSet);
        assertSame(newSet, crawlerContext.getRobotsTxtUrlSet());
        assertEquals(1, crawlerContext.getRobotsTxtUrlSet().size());

        // Set null
        crawlerContext.setRobotsTxtUrlSet(null);
        assertNull(crawlerContext.getRobotsTxtUrlSet());
    }

    /**