Added to official ideas list at http://drupal.org/node/234712
(Draft SoC 2008 project proposal)
Drupal will be using simpletest for php functional and unit testing, but currently we have no equivalent framework for javascript.
This means that every time there's a minor jQuery update (or any other javascript patch to core), about six different people have to spend hours clicking around to see if anything broke.
The project should have integration with the Drupal.org issue queue and also be possible for a developer to set up locally (i.e. using open source tools). This will involve not only Drupal/php, but also javascript, jQuery and other fun stuff.
The framework must be pluggable for different OS and browsers (i.e. IE6/7, Firefox, Safari, Opera, Konqueror).
References:
http://testing.drupal.org
http://wtr.rubyforge.org/ (WATIR browser automation library, written in Ruby)
Simpletest automation was the product of a 2006 SoC project: http://drupal.org/node/58881
http://browsershots.org does a similar thing for css/markup on multiple platforms
http://groups.drupal.org/javascript
http://groups.drupal.org/unit-testing