I kept the web app and the test suite separate to show that one can use rspec and selenium-webdriver to test any kind of web app. Simply start the web app in one terminal and go run the test suite in another terminal. You can even run the test suite against your production system to make sure there were no problems with your last deploy.
Later I will write up how to use Selenium Grid combined with a VirtualBox VM to run your tests against a browser in a different operating system. [Edit: I have now written the post, here it is.] Let me know what you find confusing about selenium and maybe I’ll blog about the answer! Check out the sample app here.