module_inclusion_matcher.rb

Spec::Matchers.define :include_module do |mod|
  match do |instance|
    mod.instance_methods.inject(true) { |accum, method| accum && instance.respond_to?(method) }
  end

  failure_message_for_should do |instance|
    "expected the class #{instance.class.name} to include the module #{mod}"
  end

  failure_message_for_should_not do |instance|
    "expected the class #{instance.class.name} not to include the module #{mod}"
  end

  description do
    "expected a class to include a mod by responding to all of its methods"
  end

end