- One of the things I like about Rails is the built-in support for testing - it's almost hard not to write tests. But even if I write extensive tests (currently "Code to Test Ratio: 1:3.4" according to rake stats in a small toy project) I still feel that it's not enough. That's where Selenium comes in. It's a javascript based functional test tool that uses Fit like test scripts to test web application directly in the browser.