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4 minute read - JavaScript QUnit

Test Driven JavaScript using QUnit

Jun 6, 2008

I have a little project that I started writing in OpenLaszlo. I chose OpenLaszlo because I thought I could script it in standard JavaScript but during the development of my minor app I found a few errors with the OpenLaszlo JavaScript implementation and the project stalled. Now, having started a new job, where the development team use splendid new technologies like QUnit, and JQuery, I resurrected my app.

So I present, to you, some notes on my experience of Test Driven JavaScript using QUnit.

I class myself as a real novice with JavaScript.

Fortunately the development team gave me a quick demo of QUnit at work so I understood a little about the technology, and no better teacher than experience can help me understand, so time to dabble.

As a novice, I followed the instructions on the QUnit site and created a basic test page (called test_eprime.htm).

<script src="jquery-latest.js"></script>
<link media="screen" href="testsuite.css" type="text/css" rel="stylesheet">
<script src="testrunner.js"></script>



<h1>E-Prime JavaScript Tests</h1>
<h2 id="banner"></h2>
<h2 id="userAgent"></h2>
<ol id="tests"></ol>
<div id="main"></div>

And when viewed in a browser this gives me the joyous news that I have 0 tests of 0 failed.

Woo Hoo!

In order to support this my code folder has:

  • jquery-latest.js
    • testrunner.js
      • testsuite.css
  • test_eprime.htm (the code above)

So now I’ll create my first test. I do this by adding all my tests between the magic lines in the above test frame work html


// **** I add all my code in here ****


QUnit has the concept of modules which ‘chunk’ tests together. So I create an html formatting module, for all my HTML formatting tests.

module("HTML Formatting");

And then I’ll write my first test…

test("html char conversion", function(){

I added a new ’test’ to the set of tests. The test had the name “html char conversion”. I created the code of the test as an unnamed function. The purpose of the test? To check the function convertToHTMLIfRequired function returns &gt; when called with the parameter >

So now I save my test_eprime.htm file and reload it into FireFox.

And voila…

…my test failed. Hopefully as you expected, after all I didn’t write any code.

So off I go to my trusty text editor and create a new file called eprime.js which looks like this

 function convertToHTMLIfRequired(c){
   return '&gt;';

Run the tests again by refreshing the page in the browser. And…

Wha! Oh, I forgot to include eprime.js into my test_eprime.htm, OK, easy fix.

 <script src="testrunner.js"></script>
 <script src="eprime.js"></script>

Refresh to run the tests.


Alright! High Five! Watch as I do my “successful test passing” dance.

And so we move on.

Back into the tests and make that a little more robust…

test("html char conversion", function(){

Refresh the browser and my tests fail. As we would hope.

Eagle eyed readers will note that I got the ’expected’ and ‘actual’ parameters the wrong way around. I should have used the format…


I could blame my error on the QUnit front page which shows the following example code…

equals( "hello", value, "We expect value to be hello" );

But I’d feel petty and, since I didn’t read the manual, I take the blame.

So I go away and add more code, like a good TDD practitioner.

function convertToHTMLIfRequired(c){
   return '&lt;';

   return '&gt;';

Refresh the browser…

Woo hoo! Cue “Successful test passing” dance… and so on, and so on…

I then follow this with more TDD iterations, which worked out rather well. But so as not to bore you, I shall conclude.


The eagle eyed among you will have said “Why does it keep saying 0 tests of 0 failed, even when 1 failed?” and the answer I respond with reads “I don’t know, I haven’t read the manual yet”.

And despite the “0 tests of 0 failed”, I like:

  • this unit test harness,
    • how easy I found writing JavaScript using TDD with QUnit,
      • TDD JavaScript,
  • the fact that my IDE consists of a free text editor notepad++, and a free Browser,
    • the fact that I haven’t had to read the manual yet, and have managed to make a lot of progress,
      • that I can keep running my tests easily,
  • by loading my test page into different browers I can check for browser compatibility

More TDD JavaScript posts coming soon. Will I ever get rid of “0 tests of 0 failed”? … stay tuned thrill seekers.

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