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