How to do integration testing in Clojure?

You can use ring-mock for ring applications. An example of creating a mock handler and using it is:

(let [h (-> (POST "/some/url" [] some-resource)
            (wrap-defaults api-defaults))]
  (let [resp (h (-> (request :post "/some/url")
                    (header "content-type" "application/json")
                    (body (generate-string {:foo :bar}))))]
    (is (= 303 (:status resp)))
    (is (= "" (:body resp)))
    (is (= "http://some/place/foo" (get-in resp [:headers "Location"])))))

For d/b interation testing and side-effects, I use with-redefs to stub out the actual side-effecting function and capture and test the arguments to it are as expected. I'm not sure if this is idiomatic, but it's what I've found the easiest, e.g.

(testing "some d/b work"
  (let [insert-data (ref {})]
    (with-redefs
      [d/insert-data<! 
       (fn [db data] (dosync (alter insert-data assoc :db db)
                             (alter insert-data assoc :data data)))]
      (let [d (your-fn your-args)]
        (is (= {:some :expected-result} d))
        (is (= {:db {:some :connection-data} :data {:some :expected-data}} @insert-data))))))

You can use atoms here, historically I've had to use refs when I was testing some agents that did write-back work, and atoms didn't work in that scenario.

The main library I use is clojure.test, I only briefly dabbled with property testing using test.check so far. I used Midje for a while, but found clojure.test felt purer, but that was down to taste. Plus if you're venturing into cljs, you may as well stick with one testing framework.

I haven't any experience using core.async, but its own tests look like a good place to start.

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