Question

I’ve set up unit tests that test a fake repository and tests that make use of a fake repository.

But what about testing the real repository that hits the database ? If this is left to integration tests then it would be seem that it isn’t tested directly and problems could be missed.

Am I missing something here?

Answer 1

Well, the integration tests would only test the literal persistence or retrieval of data to and from the layer of persistence. If your repository is doing any kind of logic concerning that data (validation, throwing exceptions if an object isn’t found, etc.), that can be unit tested by faking what the persistence layer returns (whether it returns the queried object, a return code, or something else). Your integration test will assure you that the code can physically persist/retrieve data from persistence, and that’s it. Any sort of logic to test ought to belong in a unit test.

Sometimes, however, logic could exist in the persistence layer itself (e.g. stored procedures). This could be for the sake of efficiency, or it could merely be legacy code. This is harder to properly unit test, as you can only access the logic by getting to the database. In this scenario, it’d probably be best to try and move the logic to your code base as much as possible, so that it can be tested more easily. There probably exist unit testing frameworks for scenarios such as these, but I’m not aware of them (merely out of inexperience).