Hi All, I've been having fun with unit tests: http://mail.zope.org/pipermail/zope3-dev/2006-October/020757.html http://mail.zope.org/pipermail/zope3-dev/2006-October/020775.html But Jim finally pointed me in the right direction: http://mail.zope.org/pipermail/zope3-dev/2006-October/020789.html So, stacking DemoStorages sounds like exactly what I want to do, with one DemoStorage for each test layer. A couple of questions: 1. Should I do a transaction.commit() after each layer's setup, or will a DemoStorage stacked onto another DemoStorage as follows: storage = DemoStorage(base=base_storage) ...still see all changes made to the base even if they're not committed? 2. How do I go about weaving the storage into the Zope2.app() stuff? In particular: - in a layer's setUp() method, how do I replace the DB used by the current Zope2.app() with the same storage but wrapped in a new DemoStorage? - in a layer's tearDown() method, how do I toss the DemoStorage created in the layer's setUp and replace it with the original one? 3. Is storage = DemoStorage(base=base_storage) and the dance needed for question 2 going to be quicker that transaction.commit() at the end of the layer setup and transaction.abort() at the end of every unit test? cheers, Chris -- Simplistix - Content Management, Zope & Python Consulting - http://www.simplistix.co.uk