How to test business logic layer which involves data update in database

Question

I know my question looks like I am searching for some shortcut but actually I have searched a lot and couldn't find a resource to learn unit testing specially for business layer which involves data update in database.

I did get resources to learn writing unit test cases in nunit but they all were testing static data. I don't want to learn unit test writing as a beginner, I have the idea of writing unit tests in nunit, my main question is how do we test methods which involves data insert/update/delete in database? Do we actually insert data while testing? Do mocking play a role in it?

Please help me with any resource that covers specially this case.

Thanks!

Answer 1

If your business layer is written in C#, as your tag suggests, then mocking the database is the best practice. You use a mocking framework that allows you to control the data layer and write asserts that your business layer does the correct thing under controlled (mocked) responses. If you use this approach then your test will be isolated and execute very fast without any connection to the database (you should be able to execute thousands of unit test within a second.)

If your database contains a lot of business logic itself then you can unit test it in isolation, but I would not use nunit for that.

If you decide to include the database in you nunit C# business logic test then you will have to deal with connections to the database, and shared state between test. You will be in a much more complex setup and deal with more complex errors.

Here is a good resource to start with: https://www.amazon.com/Pragmatic-Unit-Testing-Nunit-Programmers/dp/0974514020