Selenium is a popular tool for testing websites across multiple browsers, and when combined with Mozilla's implementation of the WebDriver specification, it becomes possible to interact directly with Firefox itself. In this session, we'll show a simple approach to writing tests using Selenium in Python, and then demonstrate how we're taking this further to replace our existing functional UI tests for Firefox. By using Selenium, we're hoping to make contributing to these tests much easier for our community, and by pushing the tools to their limits we'll also make them rock solid.