— layout: post title: “Unit testing with Intern: part 1” date: 2013-06-17 21:47 comments: true categories: [“unit testing”,”javascript”,”intern”] —

Some time ago i read a tweet mentioning a new library to write unit tests in Javascript, Intern.

At the moment I didn’t have much time and I already had a working solution ( a combination of mocha, chai and sinon ) so I filed the information away for future reference.

Yesterday I finally had the time to try this library so I decided to create a simple example that you can download here.

First of all I created a new folder for the example and installed the library ( this step assumes you have a working node.js installation).

mkdir intern-example
cd intern-example
npm install intern

Now the intern library is installed in the node_modules folder and we can begin to work. First of all let’s create a src folder and a simple AMD module that defines two simple functions: add and diff.

mkdir src
cd src

Then create a file library.js with this content

define([],function () {
	
	var sum = function (a, b) {
    	return a + b;
	};

	var diff = function (a, b) {
    	return a - b;
	};    

	return {
    	sum : sum,
    	diff: diff
	};
});

This is the example library we are gonna test with Intern ( nothing complicated it’s just a simple AMD module to have something working).

Now let’s create a tests folder and copy the example  intern configuration file.

mkdir tests ;
cp node_modules/intern/tests/example.intern.js tests/intern.js

Now we are ready to write our first test. Intern uses the chai library to define the assertions so I opted for my preferred style, should. The test are really simple and are meant just as examples:

define([
	'intern!bdd',
	'intern/chai!should',
	'../src/library'
], function (bdd, should, library) {
	should();
	with (bdd) {
    	describe("sum", function () {
    	    it("should sum two numbers", function () {
            	library.diff(3, 2).should.equal(1);
        	});
    	});
	}
});

The next step is to configure intern to load this file and try to run them. First of all open the intern configuration file we copied before and replace the suites line with

suites: ["tests/test"],

Save the modifications and you are ready to launch the tests on the command line with

node node_modules/intern/client.js config=tests/intern

This is all for this simple example. One thing I really like of this library is the fact that it can run easily both from the browser and the command line which is a big plus if you have to integrate it with a build process.