I really love (as with lots of things) how Ecto from the Elixir community handles this, you have an extra database and because Postgres has awesome transactions

I really love (as with lots of things) how Ecto from the Elixir community handles this, you have an extra database and because Postgres has awesome transactions you can even run all theses tests of your whole data layer in parallel, including any SQL. Ecto is largely a domain specific language for writing modular SQL so that helps test things too.