Selenium is a suite of tools to automate web app testing across many platforms. Cucumber is a BDD framework that allows you to write things in English (or whatever language you want, really), and have that execute as code. Put those together with webrat and rspec and you have a pretty mean stack to test your ruby on rails web application with. Sort of. I've been having some problems with it, getting it set up, but it's coming along. This isn't a…