javascript - How can I mock dependencies for unit testing in RequireJS?

Question

I have an AMD module I want to test, but I want to mock out its dependencies instead of loading the actual dependencies. I am using requirejs, and the code for my module looks something like this:

define(['hurp', 'durp'], function(Hurp, Durp) {
  return {
    foo: function () {
      console.log(Hurp.beans)
    },
    bar: function () {
      console.log(Durp.beans)
    }
  }
}

How can I mock out hurp and durp so I can effectively unit test?

Answer 1

So after reading this post I came up with a solution that use the requirejs config function to create a new context for your test where you can simply mock your dependencies:

var cnt = 0;
function createContext(stubs) {
  cnt++;
  var map = {};

  var i18n = stubs.i18n;
  stubs.i18n = {
    load: sinon.spy(function(name, req, onLoad) {
      onLoad(i18n);
    })
  };

  _.each(stubs, function(value, key) {
    var stubName = 'stub' + key + cnt;

    map[key] = stubName;

    define(stubName, function() {
      return value;
    });
  });

  return require.config({
    context: "context_" + cnt,
    map: {
      "*": map
    },
    baseUrl: 'js/cfe/app/'
  });
}

So it creates a new context where the definitions for Hurp and Durp will be set by the objects you passed into the function. The Math.random for the name is maybe a bit dirty but it works. Cause if you'll have a bunch of test you need to create new context for every suite to prevent reusing your mocks, or to load mocks when you want the real requirejs module.

In your case it would look like this:

(function () {

  var stubs =  {
    hurp: 'hurp',
    durp: 'durp'
  };
  var context = createContext(stubs);

  context(['yourModuleName'], function (yourModule) {

    //your normal jasmine test starts here

    describe("yourModuleName", function () {
      it('should log', function(){
         spyOn(console, 'log');
         yourModule.foo();

         expect(console.log).toHasBeenCalledWith('hurp');
      })
    });
  });
})();

So I'm using this approach in production for a while and its really robust.