команда рельсов не работает

Я следил за этим руководством., который охватывает TDD с использованием rspec, capybara и т. д. Я добавил следующее в свой Gemfile:

group :test, :development do
    gem 'turn'
    gem 'rspec-rails'
    gem 'capybara'
    gem 'guard-rspec'
    gem 'growl_notify'
end

Запустил bundle install и теперь получаю:

juco@jucoiMac ~/Desktop/rails-test $ rails s
    gem install minitest
    /Library/Ruby/Gems/1.8/gems/turn-0.9.6/lib/turn/minitest.rb:9:in `require': no such file to load -- minitest/unit (LoadError)
        from /Library/Ruby/Gems/1.8/gems/turn-0.9.6/lib/turn/minitest.rb:9
        from /Library/Ruby/Gems/1.8/gems/turn-0.9.6/lib/turn.rb:13:in `require'
        from /Library/Ruby/Gems/1.8/gems/turn-0.9.6/lib/turn.rb:13
        from /Library/Ruby/Gems/1.8/gems/bundler-1.2.4/lib/bundler/runtime.rb:68:in `require'
        from /Library/Ruby/Gems/1.8/gems/bundler-1.2.4/lib/bundler/runtime.rb:68:in `require'
        from /Library/Ruby/Gems/1.8/gems/bundler-1.2.4/lib/bundler/runtime.rb:66:in `each'
        from /Library/Ruby/Gems/1.8/gems/bundler-1.2.4/lib/bundler/runtime.rb:66:in `require'
        from /Library/Ruby/Gems/1.8/gems/bundler-1.2.4/lib/bundler/runtime.rb:55:in `each'
        from /Library/Ruby/Gems/1.8/gems/bundler-1.2.4/lib/bundler/runtime.rb:55:in `require'
        from /Library/Ruby/Gems/1.8/gems/bundler-1.2.4/lib/bundler.rb:128:in `require'
        from /Users/juco/Desktop/rails-test/config/application.rb:7
        from /Library/Ruby/Gems/1.8/gems/railties-3.2.12/lib/rails/commands.rb:53:in `require'
        from /Library/Ruby/Gems/1.8/gems/railties-3.2.12/lib/rails/commands.rb:53
        from /Library/Ruby/Gems/1.8/gems/railties-3.2.12/lib/rails/commands.rb:50:in `tap'
        from /Library/Ruby/Gems/1.8/gems/railties-3.2.12/lib/rails/commands.rb:50
        from script/rails:6:in `require'
        from script/rails:6

Когда я пытаюсь выполнить любые команды rails, включая rails server. Это было опубликовано раньше, но остался без ответа.