shoulda installation troubles

I cannot manage to have shoulda working. I'm using rvm with rails 3.1 and ruby 1.9.2 I added group :test do   gem "shoulda" end

to the Gemfile, and then run bundle install, thus the gem is installed, and it is featured in the list running gem list --local.

but whenever I add something like class ModelTest < Test::Unit::TestCase   should_not allow_value("blah").for(:email) end in a testfile, running that test with ruby -Itest test/unit/model_test.rb I get an error undefined method `allow_value' for ModelTest:Class Am I missing something? should I manually require shoulda? where and how? thanks