Question

I’m watching this video post (by Jon Galloway and Jesse Liberty) about Building a repository for testing, and they mentioned it’s not a good idea to have the DB, and rather one should use a fake repository. The two reasons they gave for that are:
1. The DB may not be available, and
2. Unit tests should be focused at the code level.

So about the first, I never encountered a scenario where I wanted to work on anything and test env. DB wasn’t available, and the second point they made I didn’t get.

So is it a bad practice using your DB in unit tests? What is the potential harm?

Thanks.

Answer 1

Unit tests should test one thing and have no external dependencies (i.e. test in isolation).

As soon as the file system or a database, or anything external is involved, it is really an integration test.

If a unit test relies on an external dependency, it requires a known state and therefore becomes prone to breaking (fragile).

As @Darin mentions, you can include a Database in an integration test by ensuring a known state by restoring a known database state, running a test in a transaction and rolling back the transaction at the end of the test.