Since Rails 3.1 Coffee-Rails is included in the default Gemfile when you create a new application. If you are upgrading to Rails 3.1 you must add the coffee-rails to your Gemfile:
If you are precompiling your assets (with rake assets:precompile) before run your application in production, you might want add it to the assets group to prevent the gem being required in the production environment. Note that this may prevent you from using Coffeescript for UJS responses.
group :assets do gem 'coffee-rails' end
$ bundle install $ bundle exec rake test
If you need to test against local gems, use Bundler's gem :path option in the Gemfile.