Setting up Mocha testing with Coffeescript, Node.js, and a Cakefile

I’m still in a Javascript (well, Coffeescript) kick. In an attempt to be productive while I train with great discipline, I decided to port Paul Dix’s Domainatrix Ruby gem into a Node module.

I really like the syntax and polish of the Mocha test framework. It spoke to me. I also use the Chai assertion module.

Objectives

• Run all tests with cake test
• A test_helper.coffee file loaded before my tests to DRY them up
• Hook in to the convetion of also making npm test run my tests

Directory structure

    /
    |-- lib  
    |    +-- (Compiled Javascript)
    |-- src  
    |    +-- (Coffeescript)
    |-- test
    |    |-- test_helper.coffee
    |    +-- (Other tests)
    |-- package.json
    |-- Cakefile

Mocha expects a test/ directory. When you run mocha, it runs all the tests found there.

The Cakefile

    # Cakefile

    {exec} = require "child_process"

    REPORTER = "min"

    task "test", "run tests", ->
      exec "NODE_ENV=test 
        ./node_modules/.bin/mocha 
        --compilers coffee:coffee-script
        --reporter #{REPORTER}
        --require coffee-script 
        --require test/test_helper.coffee
        --colors
      ", (err, output) ->
        throw err if err
        console.log output

The breakdown:

• NODE_ENV=test forces the test environment. Among other things, it lets us reset assured that tests will use the test database (which will be trashed)
• --compilers coffee:coffeescript lets Mocha know it’ll be compiling and running .coffee tests
• --reports #{REPORTER} sets the test output mode. I like “min” because it clears the screen between tests
• --require coffee-script lets us write our test_helper with Coffeescript
• --require test/test_helper.coffee loads our test_helper before our tests are run
• --colors forces output colors since Mocha disables them when it doesn’t think it’s printing to a terminal

I tried to add a test-w test that would include Mocha’s --watch and --growl options, but I couldn’t get the watcher to actually work.

The Test Helper

    # test/test_helper.coffee

    global.assert = require("chai").assert

Rather than having to declare assert = require("chai").assert in every test, I attach the assert function to the global variable that persists across my tests.

package.json

Nodejitsu has a helpful package.json cheatsheet.

    {
      ...
      "scripts": {
        "test": "cake test"
      },
      "devDependencies": {
        "chai": "~1.0.3",
        "mocha": "~1.1.0"
      },
      ...
    }

Note: npm install --save chai mocha will automatically add them to the dependencies hash along with their version number. From there you can move them into devDependencies.

The scripts hash tells Node what commands to run. For example, now npm test simply calls our Cakefile task. It seems to be the convention along with creating an npm server command. Basically, developers that clone/install your project shouldn’t have to hunt for the magical command that happens to run your test suite and start your server.

But npm test adds Node’s error output after your test output so I don’t use it.

That’s it

I hope to get Mocha’s watcher working soon so I don’t have to manually run my tests. I’ll update this post if I figure it out.