thoughtbot/shoulda-matchers — pull request #132 by mike-burns (2012-07-11 10:19:12+00:00)
Title: Mix RSpec with Test::Unit

An edge case occurs when mixing RSpec and Test::Unit tests and also
loading both the 'rspec-rails' gem and 'shoulda-matchers' gem from the
same Gemfile group, namely [:test, :development] . Work around this by
always inserting the shoulda matchers into Test::Unit, regardless of
whether RSpec is loaded.