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JavaScript Testing and Continuous Integration Part I

Adding your Tests into a continuous integration system for test automation is quite common among professional software development. However, when it comes to testing JavaScript code, many people lack the experience and best practices to set up a productive infrastructure. We at pidoco have invested quite some time to solve this problem and came up with the setup I describe in this blog post.

The JavaScript Testing Framework

There are countless frameworks out there to use for testing JavaScript code. And I have to admit it is quite confusing to find the best for one’s project. From what I saw up to now, many frameworks look very similar to each other. They do differ in some details, which make people like one or the other. To us, it was important to have a comprehensive documentation of the frameworks capabilities. Therefore, we chose the Yahoo UI test framework. It comes with an extensive documentation, just as you know from the Yahoo UI framework. You can transform a JavaScript Object into a test case, which makes it looking quite similar to JUnit tests:

var testCase = new Y.Test.Case({

    name: "TestCase Name",

    //traditional test names
    testSomething : function () {

    testSomethingElse : function () {

Within your test functions you have a broad variety of assertions that you can use. In addition, you can use the wait() and resume() functions to interrupt a test and wait for asynchronous events to happen. This is very useful if you need to wait for some UI components to be rendered or some server calls to return. Next, you can also trigger dom events using the YUI Event object:


Once you have written your first test case you want to execute the test and review the results. YUI Test comes with a nice test result viewer that you may include into your test site. On the other hand, the tests should be executed in several browsers and you may want to review the results on just one page. Therefore, the framework offers a function to send the result to a URL where a server may collect and show the results. In our first attempt we sent the result as a JSON string to the server, who transformed the collected results in a simple table with the tests in rows and the browsers in columns.

var reporter = new Y.Test.Reporter("http://www.yourserver.com/path/to/target",

Since many continuous integration servers like to read test results in an xml file, YUI allows for several formats to get your results:

  • Y.Test.Format.XML (default)
  • Y.Test.Format.JSON
  • Y.Test.Format.JUnitXML
  • Y.Test.Format.TAP

Oh, and if you asked yourself ‘where the heck is this Y coming from?”, here is the solution:

var Y = YUI();

Being able to write a JavaScript unit or integration test the next question is coming up:

How to test your web app

Following a test driven development a lot of JavaScript has to be written just for the tests. When deploying the web app into the productive environment, we don’t want to include the testing code. But how to separate testing code from productive code? We found two solutions to be possible. First, we use a plugin that loads, triggers, and reports the tests, but is only included into the system during development and test. This way, we simply disable the plugin and have a productive system without any testing code. However, not every web app has a plugin system that supports this solution. Therefore, we have thought of a second way to test your app: deploy a second app that contains a simple HTML page which loads the testing code plus an iFrame containing the web app to be tested.

Please have in mind the same origin policy for the HTML page containing the iFrame and the content of the iFrame. If both are delivered from the same domain, the outer page may access the JavaScript code of the iFrame content. This enables us to call the productive code from the testing code. In case your code either of the application or the test checks for e.g. instances of Array, it fails if the array was created inside the iFrame and checked outside or vice versa. You may create an array using new window.frames[0].Array() and test for an array with a instanceof window.frames[0].Array.

Using the iFrame approach you may enhance the HTML page such that it loads you app and the test code, automatically runs the tests, and listening to the Y.Test.Runner.COMPLETE_EVENT to upload the test result to your reporting server.

How the tests are triggered in different browsers and how this goes with continuous integration is subject of the second part of this blog post.

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  • […] I published the second part of a double blog post on JavaScript testing (first part) and how automated tests can be integrated into a continuous integration server (second […]

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