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

Question

I am trying to understand how to develop stand-alone Javascript code. I want to write Javscript code with tests and modules, running from the command line. So I have installed node.js and npm along with the libraries requirejs, underscore, and mocha.

My directory structure looks like this:

> tree .
.
├── node_modules
├── src
│   └── utils.js
└── test
    └── utils.js

where src/utils.js is a little module that I am writing, with the following code:

> cat src/utils.js 
define(['underscore'], function () {

    "use strict";

    if ('function' !== typeof Object.beget) {
        Object.beget = function (o) {
            var f = function () {
            };
            f.prototype = o;
            return new f();
        };
    }

});

and test/utils.js is the test:

> cat test/utils.js 
var requirejs = require('requirejs');
requirejs.config({nodeRequire: require});

requirejs(['../src/utils'], function(utils) {

    suite('utils', function() {
        test('should always work', function() {
            assert.equal(1, 1);
        })
    })

});

which I then try to run from the top level directory (so mocha sees the test directory):

> mocha

node.js:201
        throw e; // process.nextTick error, or 'error' event on first tick
              ^
Error: Calling node's require("../src/utils") failed with error: ReferenceError: define is not defined
    at /.../node_modules/requirejs/bin/r.js:2276:27
    at Function.execCb (/.../node_modules/requirejs/bin/r.js:1872:25)
    at execManager (/.../node_modules/requirejs/bin/r.js:541:31)
    ...

So my questions are:

• Is this the correct way to structure code?
• Why is my test not running?
• What is the best way to learn this kind of thing? I am having a hard time finding good examples with Google.

Thanks...

[sorry - momentarily posted results from wrong code; fixed now]

PS I am using requirejs because I also want to run this code (or some of it) from a browser, later.

Update / Solution

Something that is not in the answers below is that I needed to use mocha -u tdd for the test style above. Here is the final test (which also requires assert) and its use:

> cat test/utils.js 

var requirejs = require('requirejs');
requirejs.config({nodeRequire: require});

requirejs(['../src/utils', 'assert'], function(utils, assert) {

    suite('utils', function() {
        test('should always work', function() {
            assert.equal(1, 1);
        })
    })

});
> mocha -u tdd

  .

  ✔ 1 tests complete (1ms)

Answer 1

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.