CoffeeScript build setup that supports unit testing?

I'm currently using:

• Mocha as the test runner and should.js for assertions;
• Mockery to intercept certain require calls for isolated testing with mocks/stubs of required libraries;
• *JSCoverage for instrumenting the code for code coverage reports.

My code lives in src/ and I write my tests in CoffeeScript. I use make to build and test the code.

• make build compiles the CoffeeScript in src/ to JavaScript in lib/.
• make test builds the code and then runs the tests in test/.
• make monitor watches and runs the tests as soon as they change. Unfortunately it doesn't recompile the code. I use a Vim keybinding to call make, which also triggers Mocha to re-run the tests. Edit: If this bothers you, you could run coffee --watch -o lib/ -c src/.
• make coverage generates a code coverage report and puts it in lib-cov/report.html.

My Makefile looks somewhat like this:

COFFEE = ./node_modules/.bin/coffee --compile
MOCHA = NODE_ENV=test ./node_modules/.bin/mocha
MOCHA_OPTS = \
    --compilers coffee:coffee-script \
    --require should \
    --colors
REPORTER = spec

build:
    @$(COFFEE) --output lib/ src/

test: build
    @$(MOCHA) --reporter $(REPORTER) $(MOCHA_OPTS)

monitor:
    @$(MOCHA) --reporter min $(MOCHA_OPTS) \
    --watch --growl

coverage: instrument
    @MYLIB_COV=1 $(MOCHA) $(MOCHA_OPTS) \
    --reporter html-cov > lib-cov/report.html

instrument: build
    @rm -rf ./lib-cov
    @jscoverage ./lib ./lib-cov

.PHONY: build test monitor coverage instrument

You could probably use the above with very little modification.

To generate the coverage report with make coverage, the tests must be run against the instrumented code in lib-cov/ instead of the code in lib/. To make this possible, three things are needed:

1. The Makefile should set an environment variable, like MYLIB_COV (change the name as you like).

2. Your index.js should look at this environment variable and require either lib/ or lib-cov/ accordingly:

   // index.js
   module.exports = process.env.MYLIB_COV
     ? require('./lib-cov/mylib')
     : require('./lib/mylib');
   

   If you need exports from multiple source files, you can combine them here. If you have something other than index.js as 'main' in your package.json, don't forget to change it.

3. Your tests should require '../':

   # test/test.user.coffee
   describe 'User', ->
     User = {}
   
     before ->
       {User} = require '../'
   
     describe '#equals()', ->
       describe 'when users have the same username and host', ->
         it 'should return true', ->
           user1 = new User 'user', 'some.host.foo'
           user2 = new User 'user', 'some.host.foo'
           user1.equals(user2).should.be.true
   
     # etc.
   

I'll leave it as an exercise to the reader to find out whether they need Mockery and how to use it if they do. I will point out, though, that the require call in the test snippet above is done inside before for a reason.

Happy coding!