super.setUp();
        notificationHelper = new NotificationHelper();
    }

    public void test_sendToSlack_withBlankWebhookUrls() {
        // Setup mock configuration with blank webhook URLs
        ComponentUtil.setFessConfig(new MockFessConfig() {
            @Override
            public String getSlackWebhookUrls() {
                return "";
            }
        });

    /** Property key for Slack webhook URLs configuration. */
    public static final String SLACK_WEBHOOK_URLS_PROPERTY = "slack.webhook.urls";

    /** Property key for Google Chat webhook URLs configuration. */
    public static final String GOOGLE_CHAT_WEBHOOK_URLS_PROPERTY = "google.chat.webhook.urls";

    /** Property key for browser locale usage in search configuration. */

* The webhook admission plugin now works even if the API server and the nodes are in two separate networks,for example, in GKE.
The webhook admission plugin now lets the webhook author use the DNS name of the service as the CommonName when generating the server cert for the webhook.
Action required:

* Audit events now log the existence and patch of mutating webhooks.  ([#77824](https://github.com/kubernetes/kubernetes/pull/77824), [@roycaihw](https://github.com/roycaihw))
        * At Metadata audit level or higher, an annotation with key "mutation.webhook.admission.k8s.io/round_{round idx}_index_{order idx}" gets logged with JSON payload indicating a webhook gets invoked for given request and whether it mutated the object or not.

- Changed apiserver to treat failures decoding a mutating webhook patch as failures to call the webhook so they trigger the webhook failurePolicy and count against metrics like `webhook_fail_open_count` ([#131627](https://github.com/kubernetes/kubernetes/pull/131627), [@dims](https://github.com/dims)) [SIG API Machinery]

- Added support for CEL expressions to `v1alpha1 AuthorizationConfiguration` webhook `matchConditions`. ([#121223](https://github.com/kubernetes/kubernetes/pull/121223), [@ritazh](https://github.com/ritazh))

- Ignore context canceled from validate and mutate webhook ([#120020](https://github.com/kubernetes/kubernetes/pull/120020), [@divyasri537](https://github.com/divyasri537)) [SIG API Machinery]

- Kube-apiserver: timeouts configured for authorization webhooks in the --authorization-config file are now honored, and webhook timeouts are accurately reflected in webhook metrics with result=timeout ([#125552](https://github.com/kubernetes/kubernetes/pull/125552), [@liggitt](https://github.com/liggitt)) [SIG API Machinery, Auth and Testing]

- Ignore context canceled from validate and mutate webhook ([#120017](https://github.com/kubernetes/kubernetes/pull/120017), [@divyasri537](https://github.com/divyasri537)) [SIG API Machinery]

- kube-apiserver: Promoted `AuthorizeWithSelectors` feature to beta, which includes field and label selector information from requests in webhook authorization calls. Promoted `AuthorizeNodeWithSelectors` feature to beta, which changes node authorizer behavior to limit requests from node API clients, so that each Node can only get / list / watch its own Node API object, and can also only get...