gistfile1.rb

# template for Spec Matcher
Spec::Matchers.define :be_an_alien do |planet|
  match do |creature|
    creature.alien_of?(planet)
  end
  
  failure_message_for_should do |creature|
    "expected that #{creature} would be an alien of #{planet}"
  end
  
  failure_message_for_should_not do |creature|
    "expected that #{creature} would not be an alien of #{planet}"
  end

  description do
    "be an alien of #{planet}"
  end
end