Here's Alistair Cockburn's lightning talk on "Command Event DTO Architecture" recorded at the Mountain West Ruby Conference 2010 by confreaks.net. He talks about how his Hexagonal Architecture has been extended by Greg Young to form a Command-Event Architecture (aka CQRS).
Mountain West Rubyconf 2010 - Alistair Cockburn - CQRS (youtube.com)
This quick how-to runs through creating a new Rails 3 application with both RSpec and Cucumber for testing (rather than Test::Unit).
Install RSpec 2
sudo gem install rspec-rails --pre
sudo gem install cucumber-rails
Create a new Rails 3 application
Ensure you have the latest version of Rails 3 installed then