Testing with Mock Objects in Rails
UPDATE: May 24th, 2007
This post is now woefully out of date; since it was written, several excellent mocking libraries have been released, and some testing frameworks include mocking functionality of their own. Watch the Four Labs blog for an updated version of this, coming soon!

Tyrant is a "meta" Rails application designed to run other Rails applications.
Recent Comments
I think that polymorphic_url(@commentable, :anchor => “comment_#{@comment.id}") should work. You can also refactor the “comment_#{@comment.id}” to a separated method, like dom_id, which returns the dom identifier of the comment.