title: Testing a ApplicationController before_filter in Rails
body: <p>I have an application that detects the subdomain on a request and sets the result to a variable.</p>
  
  <p>e.g.</p>
  
  <pre><code>before_filter :get_trust_from_subdomain
  
  def get_trust_from_subdomain
    @selected_trust = "test"
  end
  </code></pre>
  
  <p>How can I test this with Test::Unit / Shoulda?  I don't see a way of getting into ApplicationController and seeing what's set...</p>