Class reloading is generally off in the test environment; having to reload your classes between every test run would slow down your test suite quite a lot. You can change this by adding config.cache_classes = false to your test.rb environment file (you'll find this line in your development.rb file), but I wouldn't recommend this.

Selenium tests generally run slowly, with a significant startup cost, so it's difficult to use them to iterate on your code. I very much recommend you consider driving your code with unit and functional tests, use integration tests to tie together your more complex scenarios, and save Selenium for a few happy path tests, as well as for testing AJAX flows and, to a certain extent, browser compatibility.