queue.setDepth(5);
        assertEquals(Integer.valueOf(5), queue.getDepth());

        queue.setDepth(null);
        assertNull(queue.getDepth());
    }

    public void test_lastModifiedGetterSetter() {
        // Test lastModified getter/setter
        UrlQueueImpl<Long> queue = new UrlQueueImpl<>();

        Long timestamp = System.currentTimeMillis();
        queue.setLastModified(timestamp);