gistfile1.rb

#features/steps/users_steps.rb:

Given "I'm a logged in member" do
  @me = create_adult
  logged_in_as @me
end

#features/support/env.rb:

class Cucumber::Rails::World
  ...
  def logged_in_as(user)
    cookies['integration_test_user'] = user.id.to_s
  end
  ...
end

#app/controllers/application.rb

class ApplicationController < ActionController::Base
  ...
  before_filter :login_integration_test_user, :if => lambda { Rails.env == 'test' }
  ...
  def login_integration_test_user
    return true if cookies['integration_test_user'].blank?
    integration_test_user_id = cookies['integration_test_user'].to_i

    if integration_test_user_id != current_user.id
      reset_session
      self.current_user = User.find(integration_test_user_id)
    end

    cookies['integration_test_user'] = nil
  end
end