urlQueueService.insert(urlQueue);

        // Poll should return the item
        final OpenSearchUrlQueue polled = urlQueueService.poll(sessionId);
        assertNotNull(polled);
        assertEquals("http://www.example.com/page1", polled.getUrl());
        assertEquals(sessionId, polled.getSessionId());

        // Second poll should return null (queue is empty)

        final Queue<OpenSearchUrlQueue> crawlingQueue = queueHolder.crawlingQueue;

        OpenSearchUrlQueue urlQueue = waitingQueue.poll();
        if (urlQueue == null) {
            synchronized (queueHolder) {
                urlQueue = waitingQueue.poll();
                if (urlQueue == null) {
                    final List<OpenSearchUrlQueue> urlQueueList = fetchUrlQueueList(sessionId);

        return decryptText(text);
    }

    /**
     * Polls an encryption cipher from the queue, creating a new one if none are available.
     *
     * @return an encryption cipher
     */
    protected Cipher pollEncryptoCipher() {
        Cipher cipher = encryptoQueue.poll();
        if (cipher == null) {
            try {

     */
    public void test_run_noUrlsInQueue() throws Exception {
        when(urlQueueService.poll(anyString())).thenReturn(null);
        crawlerContext.setStatus(CrawlerStatus.RUNNING);
        crawlerContext.maxThreadCheckCount = 1; // Will exit after 1 check

        crawlerThread.run();

        verify(urlQueueService, times(1)).poll(anyString());
    }

    /**
     * Test run method with crawler status DONE.
     */

    sendRequest(methodName, arguments);
    Thread.sleep(DUE_DILIGENCE_MILLIS);
    assertEquals(true, invokeMethod("hasQueuedThread", this));
    assertThat(responseQueue.poll()).isNull();
  }

  /**
   * Causes this thread to call the named method, and asserts that this thread thereby waits on the
   * given condition-like object. The lock-like object must have a method equivalent to {@link

    sendRequest(methodName, arguments);
    Thread.sleep(DUE_DILIGENCE_MILLIS);
    assertEquals(true, invokeMethod("hasQueuedThread", this));
    assertThat(responseQueue.poll()).isNull();
  }

  /**
   * Causes this thread to call the named method, and asserts that this thread thereby waits on the
   * given condition-like object. The lock-like object must have a method equivalent to {@link

            }

            @Override
            public void offerAll(String sessionId, List<UrlQueue<?>> newUrlQueueList) {
            }

            @Override
            public UrlQueue<?> poll(String sessionId) {
                return null;
            }

            @Override
            public void saveSession(String sessionId) {
            }

            @Override

int maxDepth = -1               // Max depth (-1 = unlimited)
long maxAccessCount = 0         // Max URLs (0 = unlimited)
```

### CrawlerThread (`CrawlerThread.java`)

Worker thread for crawling.

**Flow**: Poll URL → Validate → Get client → Delay → Check last-modified → Execute → Process → Extract children → Queue children → Delay

### CrawlerClientFactory

Pattern-based client selection using `LinkedHashMap<Pattern, CrawlerClient>`.

        mockQueue.add(urlQueue);

        when(dataHelper.getUrlQueueList(sessionId)).thenReturn(mockQueue);

        // Execute
        UrlQueueImpl<Long> result = service.poll(sessionId);

        // Verify
        assertNotNull(result);
        assertEquals("https://example.com", result.getUrl());
        assertTrue(mockQueue.isEmpty());
    }

    }

    @Override
    public synchronized Map<String, Object> read() {
        while (!isFinished.get() && queue.isEmpty()) {
            addDocumentToQueue();
        }

        return queue.poll();
    }

    @Override
    public void close() {
        isFinished.set(true);
        queue.clear();
    }

    /**
     * Sets the scroll size.
     * @param scrollSize The scroll size.