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.
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.