Binarylogic Authlogic

I'm trying to write integration tests for screens that require a logged in user. I'm using Webrat too.
I've added the following to test_helper

require 'authlogic/test_case'

And to my integration test:

  def setup 
    activate_authlogic
    UserSession.create! Factory.build(:user)
  end

The problem is that the session isn't maintained and my tests end up back at the login screen. I've confirmed that UserSession is created by checking the following in my tests:
UserSession.find (shows a valid UserSession instance)
UserSession.find.record (shows a valid User instance)
I've traced this back to current_user_session which is returning nil in application controller causing require_user to fail. In application_controller UserSession.find gives nil so somehow the session object is created fine in my tests but is lost in the controller.

My test just contains the following for now:

    visit '/clients'
    assert_contain 'Clients'

I'm using:
Authlogic 2.0.13
Rails 2.3.2
Webrat 0.4.4

Many thanks
David