RSpec Expectations
rspec-expectations adds should and should_not to every object and includes
RSpec::Matchers, a library of standard matchers.
Matchers
Matchers are objects used to compose expectations:
result.should eq("this value")
In that example, eq("this value") returns a Matcher object that
compares the actual result to the expected "this value".
Contribute
See http://github.com/rspec/rspec-dev