Automated testing within Drupal should be done with SimpleTest, and this module has been designed to make testing of Drupal easier for all. Its features are powerful, and create a Drupal-specific testing API which is modeled after the SimpleTest PHP library. It should be noted that as of the 6.x-2.x release of this module, and Drupal 7 core, the aforementioned third-party library is no longer a dependency.

Which version should I use?
If you are just starting to write tests for Drupal 6, you should use the 2.x branch of this module. If you have written tests previously please read the documentation, as some things have changed between versions 1.x and 2.x.

Looking forward
SimpleTest 7.x development has been moved to a new location in core! Any issues related to Drupal HEAD should be filed in the core issue queue, any issues related to tests for 7.x should be filed in their parent module's component.

SimpleTest 7.x-2.x
The branch will contain an up-to-date fork of the Drupal 7 SimpleTest module that will allow for work to continue during the Drupal 7 cylce. An external git repository is being used in order to facility easy merges with Drupal 7 core. CVS will always have the lastest development copy for use. Please see the CHANGELOG for a listing or changes made.

Take a look at Switcheroo so you can switch back and forth between core SimpleTest and SimpleTest 2.x.

The php-curl library is required for SimpleTest to function.

Further reading

Supporting organizations: 

Project information