[stubish]

One approach we used was to wrap the connections in a proxy (easy in Python), and flag if the code called the commit() method at any point. You do need to trust that the code doesn't call COMMIT explicitly via the execute() method, and flag tests running subprocesses that might dirty the database. If the test is dirty, rebuild the test database from the template instead of relying on rolling back the transactions.

However, if you add this behavior to an existing test suite you will likely have to fix a lot of tests assuming sequences will return predictable numbers, such as in automatically generated primary keys. Technically, these tests are already broken even if it is unlikely to see them fail.