Mocking in Unit Tests

The main focus of unit tests in a web application are the handler functions, passing requests to those functions and checking the responses.

All handler functions are passed a request object by default when using compojure defroutes function for routing.

If handler functions do not use arguments then you can test those handlers by simply passing an empty hash-map, {}.

For all other handler functions you can pass a request object or just specific parts of a request in a hash-map.

Ring mock library

ring-mock is a small library creating Ring request maps (Clojure hash-maps) to support unit testing. Generated hash-maps are examples of a ring request and used as arguments when calling the handler functions in tests.

Add dev dependency

As ring-mock is a development only library, it should be added to an alias not included in the packaging of the project for production.

Edit the project deps.edn file in the project and add ring-mock to an alias called :env/dev, creating the alias if required.

  :env/dev
  {:extra-deps {ring/ring-mock {:mvn/version "0.4.0"}}}

Add namespace

Add the ring-mock.request namespace to any of the test namespaces mocking of requests will be useful.

Edit the test/practicalli/status-monitor-service.clj and add ring-mock as a required namespace in files ns form.

(ns practicalli.status-monitor-service-test
  (:require [clojure.test :refer [deftest is testing]]
            [ring.mock.request :as  mock]
            [practicalli.status-monitor-service :as status-monitor]))

Add unit tests to check the handlers (which are going to be added next - TDD style)

(deftest test-app
  (testing "main route"
    (let [response ((status-monitor/app) (request :get "/"))]
      (is (= 200 (:status response)))))

  (testing "not-found route"
    (let [response ((status-monitor/app) (request :get "/invalid"))]
      (is (= 404 (:status response))))))

Examples

• API: ring-mock

(deftest your-handler-test
  (is (= (your-handler (mock/request :get "/doc/10"))
         {:status  200
          :headers {"content-type" "text/plain"}
          :body    "Your expected result"})))

(deftest your-json-handler-test
  (is (= (your-handler (-> (mock/request :post "/api/endpoint")
                           (mock/json-body {:foo "bar"})))
         {:status  201
          :headers {"content-type" "application/json"}
          :body    {:key "your expected result"}})))