Unit-testing side-effects in Clojure

clojure, side-effects, unit-testing

Solution

Using `core.test` I usually go the way of mocking up the side effectish functions using `with-redefs`

(deftest ampq-messaing
  "Test messaging"
  (let [logit-msg (atom nil)]
    (with-redefs [mq/get-message (fn [] "message")
                  logit (fn [msg] 
                           (reset! logit-msg msg))]
      (let [response (your-test-trigger)]
        (is (= "message" @logit-msg))))))

In that case I'm testing the returned message from `mq` is the one used in `logit`, and I'm assuming that `your-test-trigger` is something that triggers a call to `get-message`.

Problem

I have a function that pulls messages from an AMPQ message bus: ``` (defn get-message [queue client] (let [msg (mq/get-message client queue)] (if msg (logit msg)))) ``` mq/get-message and logit are both side-effects, one depends on network access, the other on disk IO on the local machine. Is there an idiomatic way of unit-testing side-effects in Clojure? My first thought was mocks/stubs, but if there was something better.

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