I've come up with a solution for this: I can't erase containers/databases, but I can erase a zone by sending a delete followed by a create. That's fine for my purposes because all my code so far operates on a single zone. I just have to start each test with an erase, and make sure tests don't run concurrently. 

To scale this to multiple developers/devices/bots, I'd need to come up with a unique zone name for each device's tests.

—Jens