If you ever need to test an abstract base controller independently from any subclass, you'll likely need to add a route for your test. Here's one example of how to do this in Rails 3:
*UPDATE: * Thanks to the tip by Austin Putman I've updated the gist to include an example use of the excellent with_routing method.
Nice technique for longer tests. For single tests, you can also use a with_routing block
Thanks Austin! If I had known that it would have saved me a few hours. I've updated the post to show an example of how to reuse with_routing across multiple tests.
Or take a look at the controller() method in rspec-rails2... http://pivotallabs.com/users/mgehard/blog/articles/1350-using-rspec2-to-test-rails3-applicationcontroller-functionality
Very slick - thanks!