Since ActionView::TestCase is mostly used in conjunction with testing helpers. I'm proposing changing it's namespace. I've added this as a patch over on Lighthouse: hhttp://rails.lighthouseapp.com/projects/8994/tickets/442
I've also included in the patch an assertion method to aid in testing helpers (in core and in individual applications). The methods closely mirror AC's assert_tag and assert_no_tag. I've named them assert_tag_in and assert_tag_not_in. I blogged about using a method similar to this to aid in testing plugins that add AV helpers:
I also created a branch on github: http://github.com/brianjlandau/rails/commits/refactor_action_view_testcase
I'm seeking feedback of any kind in regards to this patch and enhancement.
Thanks, Brian