---
title: "Vows and CoffeeScript"
kind: article
slug: vows-and-coffeescript
created_at: 2011-06-10
tags:
  - javascript
  - bdd
  - nodejs
  - coffee-script
  - vows
  - v8
---
CoffeeScript is a really nice way to write JavaScript code. Combined
with NodeJS you are empowered by a very fast platform to develop
server-side applications. Of course, you want to test these apps as well. [Vows][1] is really
great way to do this. Unfortunately it's not straight forward (yet) to
set up NodeJS + CoffeeScript + Vows.

[1]: http://vowsjs.org
~
First off, make sure you have CoffeeScript and Vows installed. Here I
install them _globally_ so you can use the `coffee` and `vows` command
line utilities.

    npm install -g coffee-script
    npm install -g vows

Next up, in your product directory, create a directory named `test`.
Here we'll create (classic) example: `division-test.coffee`

    :::coffeescript
    vows = require 'vows'
    assert = require 'assert'

    vows
      .describe('Division by zero')
      .addBatch
        'when dividing a number by zero':
          topic: -> 42/ 0

          'we get Infinity': (topic) ->
            assert.equal topic, Infinity

        'but when dividing zero by zero':
          topic: -> 0 / 0

          'we get a value which':
            'is not a number': (topic) ->
              assert.isNaN topic

            'is not equal to itself': (topic) ->
              assert.notEqual topic, topic

      .export(module)

I'm not going to explain the intimate details of Vows here, suffice it
to say that you calculate a value and store it in `topic`. Then you
perform a set of expectations.

The magic part is the last line, `.export(module)`. In all other
examples you'll see the last command is `.run()`. This `run()` command
runs your vows immediately.

When using coffee-script, you don't want to directly run you vows, but
gather them all together, convert them to JavaScript and then have vows
run them.

With the `test/division-test.coffee` saved, try running `vows` from
your console. Here's the output from `vows --spec`:

    λ vows --spec

    ♢ Division by zero

      when dividing a number by zero
        ✓ we get Infinity
      but when dividing zero by zero we get a value which
        ✓ is not a number
        ✓ is not equal to itself

    ✓ OK » 3 honored (0.002s)

Another great tip is `vows -w`. This will keep vows running and monitor
your test files for changes. When a file changes, it will re-run your
vows for you.

Happy testing!

_Yes, I know there are issues with Coderay parsing UTF-8 characters._