Problem with Integration Test

I am trying to setup an integration test and I keep getting the following error:

ruby test/integration/portfolios_test.rb /usr/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/active_support/dependencies.rb:123:in `const_missing': uninitialized constant IntegrationTest (NameError)         from test/integration/portfolios_test.rb:3

Empty code shell for the integration test: portfolios_test.rb:

require File.dirname(__FILE__) + '/../test_helper'

class PortfolioTest < ActionController::IntegrationTestSession end

Any ideas? I am using the syntax from Recipe 43 in the Rails Cookbook.

Thanks! Asa