rspec

http://rubygems.org

doc:
http://relishapp.com/rspec/rspec-rails/docs/start-from-scratch

nice tutorial:
http://ruby.railstutorial.org/chapters

binding.pry

Best screencasts about rails: http://railscasts.com
The last episode was about pry. Nice alternative to irb.
http://pry.github.com/

How to change your editor in pry? Let's do this in Ubuntu and switch from nano to vim
Just make/add to a file named '.pryrc' in your home folder

pry -r config/environment