これを設定しようとすると、次のエラーが発生します。何が起こっているのか理解できません。Michael HartlのRailのチュートリアルに従って、最初のテストをセットアップしようとしていますが、何も機能していないようです。
C:\rails_projects\sample_app>bundle exec autotest
loading autotest/rspec2
C:/rails_projects/sample_app/.autotest:1:in `require': cannot load such file -- autotest/growl (LoadError)
from C:/rails_projects/sample_app/.autotest:1:in `<top (required)>'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/ZenTest-4.7.0/lib/autotest.rb:315:in `load'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/ZenTest-4.7.0/lib/autotest.rb:315:in `block in initialize'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/ZenTest-4.7.0/lib/autotest.rb:314:in `each'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/ZenTest-4.7.0/lib/autotest.rb:314:in `initialize'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/rspec-core-2.9.0/lib/autotest/rspec2.rb:13:in `initialize'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/ZenTest-4.7.0/lib/autotest.rb:244:in `new'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/ZenTest-4.7.0/lib/autotest.rb:244:in `run'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/ZenTest-4.7.0/bin/autotest:6:in `<top (required)>'
from C:/RailsInstaller/Ruby1.9.3/bin/autotest:19:in `load'
from C:/RailsInstaller/Ruby1.9.3/bin/autotest:19:in `<main>'