There are test frameworks which automate this behavior -- both Django and Rails provide test-case libraries which run each test in a transaction, and roll back

There are test frameworks which automate this behavior -- both Django and Rails provide test-case libraries which run each test in a transaction, and roll back to reset. (NB they also have to provide ways to disable this -- in order to, e.g., test application code which itself can conditionally roll back -- so both can also reset database state "the hard way", at a performance penalty.)