> You can extend/mock the class itself. Refactoring code is easy and cheap. There is no reason for complex abstractions that protect implantation outside of libraries and frameworks.
"Mock" can be a loaded word in this context, so please excuse me if I'm looking at it through a difference lens, but if you're using some sort of mocking set of tooling (like Jest or similar), I'd argue that those mocks are much more confusing than an interface with an implementation.
I personally love an interface because it defines the most narrow set of operations an object needs to support to be passed in, and the implementation of those are completely irrelevant for calling. In many cases, I personally find that a lot simpler and cleaner to read.
"Mock" can be a loaded word in this context, so please excuse me if I'm looking at it through a difference lens, but if you're using some sort of mocking set of tooling (like Jest or similar), I'd argue that those mocks are much more confusing than an interface with an implementation.
I personally love an interface because it defines the most narrow set of operations an object needs to support to be passed in, and the implementation of those are completely irrelevant for calling. In many cases, I personally find that a lot simpler and cleaner to read.