An example Jetty component using Stuart Sierra's component Clojure library.

http_server.clj

(ns my-project.http-server
  (:require [compojure.core :as compojure]
            [com.stuartsierra.component :as component]
            [my-project.my-resource :as my-resource]
            [ring.adapter.jetty :as jetty]))

(compojure/defroutes app
                     my-resource/handler)

(defrecord HTTPServer [port server]
  component/Lifecycle
  (start [component]
    (println ";; Starting HTTP server")
    (let [server (jetty/run-jetty app {:port port :join? false})]
      (assoc component :server server)))
  (stop [component]
    (println ";; Stopping HTTP server")
    (.stop server)
    (assoc component :server nil)))

(defn new-http-server
  [port]
  (map->HTTPServer {:port port}))

http_server_test.clj

(ns my-project.http-server-test
  (:require [my-project.http-server :refer [new-http-server]]
            [clojure.test :refer [deftest is]]
            [com.stuartsierra.component :as component]))

(def http-server (new-http-server 8080))

(deftest http-server-lifecycle
  (alter-var-root #'http-server component/start)
  (is (:server http-server) "HTTP server has been added to component")
  (is (.isStarted (:server http-server)) "HTTP server starts")
  (alter-var-root #'http-server component/stop)
  (is (nil? (:server http-server)) "HTTP server instance is removed from component"))

This won't work - it will not return a HTTPServer anymore but a plain clojure map (as you dissoc a required key from a record)

Updated per @the-kenny comment. Found a little more info here.

server does not need be a base field of HTTPServer. Then you can dissoc it from the component on stop.