data.addChildUrl(child1);
        data.addChildUrl(child2);
        assertEquals(2, data.getChildUrlSet().size());

        // Remove one child URL
        data.removeChildUrl(child1);
        assertEquals(1, data.getChildUrlSet().size());
        assertFalse(data.getChildUrlSet().contains(child1));
        assertTrue(data.getChildUrlSet().contains(child2));
    }