warden.rb

# Create a file `spec/acceptance/support/warden.rb' with the following 
# contents:

Spec::Runner.configure do |config|
  config.include Warden::Test::Helpers, :type => :acceptance
  config.after(:each, :type => :acceptance) { Warden.test_reset! }
end

# Or, if you're using RSpec 2 / Rails 3, the contents should be the following 
# instead:

RSpec.configure do |config|
  config.include Warden::Test::Helpers, :type => :acceptance
  config.after(:each, :type => :acceptance) { Warden.test_reset! }
end

your_spec.rb

# Then in your features you'll only need to call the `login_as` or `logout` 
# methods. More info here: http://wiki.github.com/hassox/warden/testing

feature "Home page" do

 background do
   @user = User.create(...) # Or use fixtures, factories or whatever, even a 
                            # stub user
   login_as @user
   visit home_page
 end
 
 # ...
end