The SQL example is a great one. I worked on a project where we used MySQL but then used SQLite for unit tests and integration tests. We technically wanted to be

The SQL example is a great one. I worked on a project where we used MySQL but then used SQLite for unit tests and integration tests. We technically wanted to be able to swap out the RDBMS to something like Postgres but in practice it was never going to happen. Over time it started getting complicated as some stuff we used in MySQL wasn't supported in SQLite. Eventually I just ditched SQLite and changed our testing to start a real MySQL server and destroy it after testing is complete.