Why do I see "define not defined" when running a Mocha test with RequireJS?

Question

The reason your test isn't running is because src/utils.js is not a valid Node.js library.

According to the RequireJS documentation, in order to co-exist with Node.js and the CommonJS require standard, you need to add a bit of boilerplate to the top of your src/utils.js file so RequireJS's define function is loaded.

However, since RequireJS was designed to be able to require "classic" web browser-oriented source code, I tend to use the following pattern with my Node.js libraries that I also want running in the browser:

if(typeof require != 'undefined') {
    // Require server-side-specific modules
}

// Insert code here

if(typeof module != 'undefined') {
    module.exports = whateverImExporting;
}

This has the advantage of not requiring an extra library for other Node.js users and generally works well with RequireJS on the client.

Once you get your code running in Node.js, you can start testing. I personally still prefer expresso over mocha, even though its the successor test framework.

The Mocha documentation is lacking on how to set this stuff up, and it's perplexing to figure out because of all the magic tricks it does under the hood.

I found the keys to getting browser files using require.js to work in Mocha under Node: Mocha has to have the files added to its suites with addFile:

mocha.addFile('lib/tests/Main_spec_node');

And second, use beforeEach with the optional callback to load your modules asynchronously:

describe('Testing "Other"', function(done){
    var Other;
    beforeEach(function(done){
        requirejs(['lib/Other'], function(_File){
            Other = _File;
            done(); // #1 Other Suite will run after this is called
        });
    });

    describe('#1 Other Suite:', function(){
        it('Other.test', function(){
            chai.expect(Other.test).to.equal(true);
        });
    });
});

I created a bootstrap for how to get this all working: https://github.com/clubajax/mocha-bootstrap

You are trying to run JS modules designed for browsers (AMD), but in the backend it might not work (as modules are loaded the commonjs way). Because of this, you will face two issues:

1. define is not defined
2. 0 tests run

In the browserdefine will be defined. It will be set when you require something with requirejs. But nodejs loads modules the commonjs way. define in this case is not defined. But it will be defined when we require with requirejs!

This means that now we are requiring code asynchronously, and it brings the second problem, a problem with async execution. https://github.com/mochajs/mocha/issues/362

Here is a full working example. Look that I had to configure requirejs (amd) to load the modules, we are not using require (node/commonjs) to load our modules.

> cat $PROJECT_HOME/test/test.js

var requirejs = require('requirejs');
var path = require('path')
var project_directory = path.resolve(__dirname, '..')

requirejs.config({
  nodeRequire: require, 
  paths: {
    'widget': project_directory + '/src/js/some/widget'
  }
});

describe("Mocha needs one test in order to wait on requirejs tests", function() {
  it('should wait for other tests', function(){
    require('assert').ok(true);
  });
});


requirejs(['widget/viewModel', 'assert'], function(model, assert){

  describe('MyViewModel', function() {
    it("should be 4 when 2", function () {
        assert.equal(model.square(2),4)
    })
  });

})

And for the module that you want to test:

> cat $PROJECT_HOME/src/js/some/widget/viewModel.js

define(["knockout"], function (ko) {

    function VideModel() {
        var self = this;

        self.square = function(n){
            return n*n;
        }

    }

    return new VideModel();
})