Joomla! Documentation™

News and Updates

2009 07 27 Document created.

Functional Testing

Functional (or system) testing is an essential part of a good Quality Control program. For a good general discussion of functional testing, visit the Wikipedia article.

Functional Testing in Open Source

Web applications have been notoriously difficult to do functional testing with. It has traditionally required a great deal of time and effort. This can be a special challenge for open source projects because testing is often not very popular and designing tests that can be executed in a systematic way even less so. For a complicated application like Joomla!, this means that although we might do testing, we very seldom are able to perform extensive testing on each release that covers even a fraction of the elements in the CMS.

Relatively recently, a project called Selenium has arrived on the scene. This project makes performing automated functional testing of web applications possible. This means that it is possible to devise a test and have it performed in an automated way without the requirement of somebody sitting in front of a browser and being a click monkey.

The benefits of functional testing are:

• Functional tests help highlight cases where changes in one element of the system might cause breakage in other, unexpected areas.
• Functional tests help clearly specify how the application should behave.

Functional Testing versus Unit Testing

In order to fully test an application, both functional and unit testing are essential. Each approach has their benefits and weaknesses. Unit testing is very good for isolating small chunks of code and ensuring that they are behaving as expected. Functional testing, on the other hand, is geared towards looking at the system as a whole and ensuring that the units are behaving together in a way that achieves the desired effect.

The advantages of functional testing is that functional tests are easier to understand and conceptualize by people who are unfamiliar with the underlying code. With Selenium, tests can be designed by people who are not overly familiar with PHP - they only need to understand the application and what results should be expected.

The downside of functional testing is that it will only tell you that something broke. It isn't as obvious with functional testing exactly what went wrong or where the problem is.

Test Objects

If the purpose of unit tests is to isolate a module of code, then the purpose of functional tests is to evaluate the entire system. This is much easier for those unfamiliar with what happens under the hood of Joomla! because one is not required to understand what happens during a Joomla! page request. A functional test might evaluate, for example, if unpublishing an article works properly. Therefore, to design the test, it is only necessary to figure out how to change an article from Published to Unpublished, and how to verify that the article was actually unpublished.

Functional Testing Testing in Joomla!

I have recently been building a functional testing architecture that will make it possible to write tests once, and to execute those tests on a variety of platforms and clients. I currently have infrastructure in place that makes it possible to run one command and execute functional tests in one browser on one host system. I have designed the host system in such a way that it will run on 6 different PHP versions (stock Ubuntu PHP 5 and self-compiled PHP 4.3, 4.4, 5.0, 5.1 and 5.2) and 2 different web servers (Apache and Lighttpd). These are all currently serving from the same database.

The future steps will be to make it possible to run on multiple host systems (the requirement for this is to generalize the code that resets the database state after the tests are run) and to make it possible to use different clients (i.e. different systems with different web browsers). These steps should be fairly trivial, but I have not yet had time to focus on them.

This will eventually make it possible to run the designed tests on every major browser and on multiple server platforms (various PHP versions, various configurations, various operating systems and various web servers).

Writing Functional Tests

Selenium IDE makes it fairly easy to write functional tests. It is a Firefox extension that operates as an Integrated Development Environment for creating functional tests. In essence, it records your clicks as you navigate in your browser and encodes them into a series of commands that can control the browser.