Clojurescript Generative Testing with clojure.spec

Generative testing with clojure.spec in Clojurescript.

Start the Shadow-CLJS server in a Docker container with

        docker-compose up

This opens a watcher on the tests. Open the test runner on http://localhost:8021 to see the status.

The src and test directories are mounted into the Docker container so you edit and see live updates when the files are saved on the host (no need to access the Docker container or rebuild it).

Common Errors with Spec on ClojureScript

The ClojureScript macro system is quite fickle compared to the Clojure implementation. The check macro suffers from this.

Here are some common errors.

Namespace aliasing does not work with check

Yes, that is right. See the core_test.cljs file for details.

(ns generative.core-test
  (:require
   [generative.core :as c]
   [clojure.test :refer-macros [deftest testing is are]]
   [clojure.test.check]
   [clojure.test.check.properties]
   [cljs.spec.alpha :as s]
   [cljs.spec.test.alpha :as stest :refer-macros [instrument check]]))

;; details elided
 
    (testing "We can call check on a namespace (using the alias)"
      (is (check (stest/enumerate-namespace 'generative.core))))

Here the check macro throws up on the aliased namespace and you will see this:

        Encountered error when macroexpanding cljs.spec.test.alpha/check.
        Error in phase :compile-syntax-check
        RuntimeException: No such namespace: stest

The workaround is to use fully qualified namespaces instead of aliases.

Require clojure.test.check and clojure.test.check.properties

I have not been able to find the root cause of this error:

        Error: Require clojure.test.check and clojure.test.check.properties before calling check.

I cannot reproduce it in small, new, toy projects, however, it does appear in some bigger projects.

One workaround seems to be to delete the .m2 Maven repository, node_modules and package-lock.json and run npm install to renew the NPM modules and the Java-siden packages when Shadow CLJS runs again.