sse_test.clj

(deftest sse
  (let [closed (promise)
        result (atom [])
        app (fn [req] 
              (as-sse-channel req
                :on-open (fn [ch]
                           (doseq [x (range 5 0 -1)]
                             (send! ch x))
                           (send! ch {:event "close", :data "bye!"})
                           (send! ch "to detect the client close")),
                :on-close (fn [ch _] (deliver closed :success))))
        server (run app)
        client (event-source "http://localhost:8080")]
    (.register client (reify EventListener
                        (onEvent [_ e]
                          (swap! result conj (.readData e))
                          (when (= "close" (.getName e))
                            (.close client)))))
    (.open client)
    (is (= :success (deref closed 5000 :fail)))
    (is (not (.isOpen client)))
    (is (= ["5" "4" "3" "2" "1" "bye!"] @result))
    (stop server)))