Faking Database Interactions with Entity Framework Core

Entity Framework (EF) Core and other object-relational mappers (ORMs) available on .NET allow us to fake the database functionality using in-memory databases. This enables us to use the same code in our application as we would use for a real database. In contrast, we don’t have to use any real database connection in unit tests, which makes our tests fast.

In the context of automated testing, this technique is called faking. Unlike stubbing and mocking, faking allows us to interact with the object the same way we would interact with a real object, (i.e., the object exhibits a realistic behavior and returns realistic responses). The object can even keep its state, which certain interactions can modify.

A fake can be represented by an external object outside our code. ...