helper.rb

module AuthenticationHelpers
  def authenticated_as(roles, options=nil)
    options = instance_eval(&options) if options.is_a? Proc

    Array(roles).each do |role|
      context "when logged in as a #{role}" do      
        before(:all) { @user = FactoryGirl.create role, *Array(options) }
        after(:all)  { DatabaseCleaner.clean }

        before(:each) { sign_in @user }
        after(:each)  { sign_out @user }

        yield if block_given?
      end
    end
  end
end