If you can't reason about your objects in isolation, how can you expect to reason about them in aggregate? I don't use my objects in isolation. Maybe I can mo

If you can't reason about your objects in isolation, how can you expect to reason about them in aggregate? I don't use my objects in isolation. Maybe I can mock up some factory which creates model objects outside of my persistence mechanism, but what value is that? I care that when I create an object in response to an action from a real user the persistence mechanism produces the correct object. I happily bulk load testing data into my persistence mechanism for testing purposes, but I see almost no reason to mock it for tests.