Selenium

Selenium is an automated software testing framework for web applications. It drives a real browser automatically, as if a real person was doing the clicking and typing. We use it here at The Economist for functional / black-box / acceptance testing, the kind of tests that are repetitive and time-consuming to step through manually. We've setup a system that runs our full suite of regression tests in parallel, using virtual machines in the Rackspace cloud, on every commit to trunk.
You want to test your Drupal code? We’ve learned how to do it, the hard way, through 3 years of experience with continuous integration at The Economist. And I can distill our current approach into a few short paragraphs: 1. Use Simpletests to unit test code. Unit testing is vital, but it’s also difficult in Drupal, because a lot of time you’re actually writing glue code, or exporting Views, or theming.