assertEquals(timestamp, queue.getLastModified());

        queue.setLastModified(null);
        assertNull(queue.getLastModified());
    }

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

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