Automated testing is one of the most significant things that you can do to improve any software project.

The Drupal project uses its own version of Simpletest for automated testing. We'll cover how to run tests and use Simpletest, and then go through the Simpletest Tutorial to explain how to write your own tests.

Selenium IDE is a Firefox add-on that records clicks, typing, and other actions to make a test, which you can play back in the browser. It can be used alone as a testing tool, but can also be used to create tests and convert them into simpletests, using the Selenium to Simpletest module. I'll demonstrate how easy it is to use Selenium IDE and convert a test created that way to a Simpletest.

Who will be interested? Anybody who can do a little PHP can write simpletests. You don't even need that to use Selenium.