Routes in Functional Tests?

I have the following:

:: generic_controller.rb ::

class GenericController < ApplicationController
  def activate
  end

  def index
  end
end

:: routes.rb ::

ActionController::Routing::Routes.draw do |map|
  map.activate '/activate/:activation_code', :controller =>
'generic', :action => 'activate'
end

:: generic_controller_test.rb ::

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

class GenericControllerTest < ActionController::TestCase
  def test_activate_path
    get :index
    assert_not_nil activate_path("something")
  end
end

0 remus test/functional % ruby generic_controller_test.rb
Loaded suite generic_controller_test
Started
.
Finished in 0.280308 seconds.
1 tests, 1 assertions, 0 failures, 0 errors

If I comment out the get :index call in my test file, I get this:

0 remus test/functional % ruby generic_controller_test.rb
Loaded suite generic_controller_test
Started
E
Finished in 0.282201 seconds.
  1) Error:
test_activate_path(GenericControllerTest):
NoMethodError: You have a nil object when you didn't expect it!
The error occurred while evaluating nil.rewrite
    /usr/lib64/ruby/gems/1.8/gems/actionpack-2.0.2/lib/
action_controller/base.rb:616:in `url_for'
    (eval):17:in `activate_path'
/usr/lib64/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/
test_process.rb:463:in `send!'
/usr/lib64/ruby/gems/1.8/gems/actionpack-2.0.2/lib/action_controller/
test_process.rb:463:in `method_missing'
    generic_controller_test.rb:7:in `test_activate_path'
/usr/lib64/ruby/gems/1.8/gems/activesupport-2.0.2-/lib/active_support/
testing/default.rb:7:in `run'

What is it about the get call that "turns on" the named route?

Regards,
--Dean