Unit Testing Google App Engine Applications - Blogs at Near Infinity

Lots of stuff out there on unit testing and mocking GAE:

http://blog.appenginefan.com/2008/06/unit-tests-for-google-app-engine-apps.html
Unit Testing Google App Engine Applications - Blogs at Near Infinity

Got this working locally:

http://appengine-cookbook.appspot.com/recipe/app-engine-test-runner/