I have a much more liberal view of what constitutes a unit test: everything that can be run inside a single container is a unit test. Writing files? Unit test.

I have a much more liberal view of what constitutes a unit test: everything that can be run inside a single container is a unit test. Writing files? Unit test. Using databases? As long as that database is started by the test fixture in the same container and destroyed along with the container, still a unit test. Of course, if your test needs a database the natural follow-up question is whether it can populate the database with data known at build time, or it needs to reach out to get some realistic looking data. Only the latter makes it an integration test.