Configure the url helpers correctly

Since
6c7d895dda
action dispatch routing helpers are only included in action view using
the railtie. Since we don't load the railtie in test environment we need
to properly setup it

test/test_helper.rb

@@ -5,6 +5,8 @@ require 'minitest/autorun'
 require 'active_model'
 require 'action_controller'
 require 'action_view'
+ActionView::RoutingUrlFor.send(:include, ActionDispatch::Routing::UrlFor)
+
 require 'action_view/template'
 
 require 'action_view/test_case'