Interfaces are not the only option - you can also mark methods as virtual. But overuse of mocking is a very big problem in a lot of codebases. Often I look at

Interfaces are not the only option - you can also mark methods as virtual. But overuse of mocking is a very big problem in a lot of codebases. Often I look at a test, and all it seems to do is setup mocks, such that I'm not sure if anything is actually being tested! My hope is that C#'s new default interface implementations feature will put an end to this mess.