In the past weeks I bumped into LotusRB from my RubyWeekly.com newsletter published by @PeterC, signup if you haven't (pun intended). After a few glances I fell in love. So i immediately setout to get my next project at work going. Lotus is very testable. And as usual in the Ruby world, there is enough rope to kill 10 newbies in one go. After a bit of enthusiasm came the realization that i'd better do things the right way and make my life easy.
There are things to test. Depending on how you like your flow. Lotus supports both MiniTest by default and RSpec as an option. Just follow the 'get started' docs and get your app going.
BDD can easily be done without hitting the DB. Capybara is included and a spec/web/features
directory is a start for you. So, assuming you are a Lotus newbie. You might want to know what you need to test.