One could add a side channel to tell it to fail certain calls. I'm doing a similar thing at work---I have a mock DB that runs with a side channel for the testi

One could add a side channel to tell it to fail certain calls. I'm doing a similar thing at work---I have a mock DB that runs with a side channel for the testing framework to tell the mock DB what to pass and what to fail (I should say I'm not testing the DB, but a program that talks to the DB).