}

    public void test_instanceOfFessSystemException() {
        // Verify that ContentNotFoundException is an instance of FessSystemException
        String parentUrl = "http://example.com/parent";
        String url = "http://example.com/child";
        ContentNotFoundException exception = new ContentNotFoundException(parentUrl, url);

        assertTrue(exception instanceof FessSystemException);

            final FailureUrlService failureUrlService = ComponentUtil.getComponent(FailureUrlService.class);
            failureUrlService.store(crawlingConfig, ContentNotFoundException.class.getCanonicalName(), url,
                    new ContentNotFoundException(urlQueue.getParentUrl(), url));
        }
    }

    /**
     * Stores a child URL in the crawling queue with duplicate host handling.