README

cypress-clojurescript-preprocessor

A Cypress preprocessor for ClojureScript, which uses Shadow CLJS for processing Cypress tests written in ClojureScript.

The plugin works by inspecting the Cypress integrationFolder (by default, cypress/integration) for ClojureScript files (*.cljs, e.g. cypress/integration/my_app/app_test.cljs -> (ns my-app.app-test)) and generates a shadow-cljs.edn configuration file with a build for each test file. This configuration is then used to compile the tests into Javascript before submitting to the browser.

The shadow-cljs server is kept running while the Cypress runner is active. When a test is run, the test file is watched for changes and a recompile is done if the test file is changed and Cypress is notified to rerun the test. The first compile is a bit slow, but subsequent compiles are fast (the plugin uses shadow-cljs compile command, which defaults to optimizations: none).

Example usage

Create a project

$ mkdir cypress-cljs-sample
$ cd cypress-cljs-sample
$ echo {} > package.json

Install Cypress
```
npm install cypress --save-dev
```

Install cypress-clojurescript-preprocessor

npm install cypress-clojurescript-preprocessor

Configure ClojureScript preprocessor

$ mkdir -p cypress/plugins
$ cat << EOF > cypress/plugins/index.js
const makeCljsPreprocessor = require('cypress-clojurescript-preprocessor');
/**
 * @type {Cypress.PluginConfig}
 */
module.exports = (on, config) => {
  on('file:preprocessor', makeCljsPreprocessor(config));
};
EOF

This will delegate files other than *.cljs to the default Browserify preprocessor. If you need to run other preprocessors, then combine them with for example:

module.exports = (on, config) => {
  const browserifyPreprocessor = makeBrowserifyPreprocessor();
  const cljsPreprocessor = makeCljsPreprocessor(config);
  // Use the default Browserify preprocessor for files other than *.cljs
  on('file:preprocessor', (file) => file.filePath.endsWith('.cljs') ? cljsPreprocessor(file) : browserifyPreprocessor(file));
};

Write test in ClojureScript

$ mkdir -p cypress/integration/examples
$ cat << EOF > cypress/integration/examples/window.cljs
(ns examples.window
  (:require-macros [latte.core :refer [describe beforeEach it]]))

(def cy js/cy)

(describe "Window"
  (beforeEach []
    (.visit cy "https://example.cypress.io/commands/window"))
  (it "cy.window() - get the global window object" []
    (.should (.window cy) "have.property" "top")))
EOF

Run test
```
./node_modules/.bin/cypress open
```

REPL in Cypress

You can active REPL into a test in the browser that Cypress is controlling.

Lookup NREPL port used by the shadow-cljs server

$ cat .preprocessor-cljs/.shadow-cljs/nrepl.port
50796

Connect to the NREPL server and list builds

shadow.user> (shadow/get-build-ids)
(:npm :local :window_foo :window)

Open a test in the Cypress runner

Start shadow-cljs watch on the test that is open in the Cypress runner

shadow.user> (shadow/watch :window)
[:window] Configuring build.
[:window] Compiling ...
[:window] Build completed. (119 files, 0 compiled, 0 warnings, 1.22s)
:watching

The build-id is a keyword of the test file name

Start a ClojureScript repl

shadow.user> (shadow/repl :window)
To quit, type: :cljs/quit
[:selected :window]
cljs.user> (js/alert "plop") ;; To try out that it works

Now you can use the slightly undocumented now command to execute Cypress command immediately, for example, to select an option:

cljs.user> (-> (.now js/cy "get" "#some-opt")
               (.then (fn [el]
                        (.now js/cy "select" el "two"))))
#object[Promise [object Promise]]

When done, exit the repl and stop shadow-cljs watch for the repl build

cljs.user> :cljs/quit
Exited CLJS session. You are now in CLJ again.
:cljs/quit
shadow.user> 
(shadow/stop-worker :window)
Worker shutdown.
:stopped

Some references to the now command:

Configuration

Shadow CLJS configuration override

The Shadow CLJS configuration used by the preprocessor may be overridden via a shadow-cljs-override.edn file, which is merged on top of the default configuration with meta-merge. By default, [mocha-latte "0.1.2"] and [chai-latte "0.2.0"] are included in the shadow-cljs.edn configuration used by the preprocessor.

Shared namespaces

The working directory of the shadow-cljs compiler that is driven by the preprocessor is the cypress folder. Because of this, in order to include shared code that is in a folder at the same level as the cypress directory, use a relative (or absolute path) e.g.

$ tree -I "node_modules" -P common.cljs\|window.cljs
.
├── cypress
│   ├── fixtures
│   ├── integration
│   │   └── examples
│   │       └── window.cljs
│   ├── plugins
│   └── support
└── src ;; shared code directory
    └── net
        └── tiuhti
            └── common.cljs
$ cat shadow-cljs-override.edn
{:source-paths ["../src"]} ;; path relative to `cypress` directory
$ head -3 cypress/integration/examples/window.cljs
(ns examples.window
  (:require-macros [latte.core :refer [describe beforeEach it]])
  (:require [net.tiuhti.common :as common]))  ;; require namespace in the `src` directory

Dependencies used by the shared code would have to be specified in the :dependencies key in shadow-cljs-override.edn file.

Development

Here's some notes on how to develop this library.

Shadow-cljs repl

The preprocessor is written in ClojureScript and compiled to a npm library with the help of shadow-cljs. To develop the library in a ClojureScript repl:

Start node repl via shadow-cljs node-repl
Connect to the nrepl server for example from Emacs with cider: cider-connect
In nrepl at the shadow.user> prompt, switch to the node repl via: (shadow/repl :node-repl)

Use locally compiled version

To use a local version of the preprocessor, point the client project to the local clone of the preprocessor:

{
  "devDependencies": {
    "cypress": "^7.6.0",
    "shadow-cljs": "^2.14.5"      ;; <-- Also, need to have shadow-cljs installed in the client project
  },
  "dependencies": {
    "cypress-clojurescript-preprocessor": "../cypress-clojurescript-preprocessor"  ;;  <-- Directory of the local copy
  }
}

Note the the client project also needs shadow-cljs to be installed (apparently :)).

Then, compile your changes via

$ npm run prepare

And (re)start Cypress in the client project:

$ ./node_modules/.bin/cypress open

Changelog

0.2.0
- Support REPL in an open test, allows to use the "now" command
- Finally fix zombie processes after exit, by using signal-exit, thanks to this blog post
- Detech shadow-cljs startup by polling port/pid files and remove race condition around subprocess stdout/stderr
0.1.7
- Bump shadow-cljs to 2.14.5
- Call process/exit to not leave zombies when Cypress exits
- When adding a new test while the preprocessor is running
  - Use same optimization level as for initial build config
  - Prevent duplicate merge of shadow-cljs-override.edn
0.1.6 Support namespaces with multiple segments (thanks @martinklepsch !), also files with underscore. Bump chokidar to 3.5.2
0.1.5 Merge override config ontop final config, allows to add additional :source-paths
0.1.4 Bundle browserify preprocessor
0.1.3 Add shadow-cljs-override.edn
0.1.2 Bundle Bundle mocha-latte and chai-latte
0.1.0 Initial release

Usage no npm install needed!