Sebastian Bergmann has a quick note today on his blog about an article from IBM that taks about using unit testing, specifically PHPUnit.

IBM DeveloperWorks has an article titled "Check your PHP code at every level with unit tests" that suggests unit tests for PHP code at the module, database, and user-interface levels and proposes IBM not only uses my software, but also advocates it.

You can find out complete information on PHPUnit from the project homepage and about unit testing from here.