// assertTrue(indexUpdater.finishCrawling);
    }

    // Test addFinishedSessionId
    public void test_addFinishedSessionId() {
        final String sessionId = "session123";
        indexUpdater.addFinishedSessionId(sessionId);
        assertTrue(indexUpdater.finishedSessionIdList.contains(sessionId));
    }

    // Test addFinishedSessionId with multiple sessions
    public void test_addFinishedSessionId_multiple() {

                        crawlerStatusList.set(i, Constants.DONE);
                        final String sid = crawlerList.get(i).getCrawlerContext().getSessionId();
                        indexUpdater.addFinishedSessionId(sid);
                        activeCrawlerNum--;
                    }
                }
                ThreadUtil.sleep(crawlingExecutionInterval);
            }

     * This method is thread-safe and adds the session ID to be cleaned up later.
     *
     * @param sessionId the crawler session ID that has finished processing
     */
    public void addFinishedSessionId(final String sessionId) {
        synchronized (finishedSessionIdList) {
            finishedSessionIdList.add(sessionId);
        }
    }

    /**