async_test.clj

(deftest websocket-from-servlet
  (let [path "/test-servlet"
        events (atom [])
        result (promise)
        handler (fn [req]
                  (as-channel req
                    {:on-open    (fn [_]
                                   (swap! events conj :open))
                     :on-close   (fn [_ {c :code}]
                                   (deliver result (swap! events conj c)))
                     :on-message (fn [_ m]
                                   (swap! events conj m))}))
        servlet (create-servlet handler)]
    (try
      (run servlet {:path path})
      (let [socket (ws/connect (str "ws://localhost:8080" path))]
        (ws/send-msg socket "hello")
        (ws/close socket))
      (is (= [:open "hello" 1001] (deref result 2000 [:fail])))
      (finally
        (stop {:path path})))))