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Before Mockito, it was common (where I worked) to create an interface just to support testing. This is an anti-pattern in my opinion. To create interfaces just for testing complicates the code and it is one of my pet peeves. It also encourages the factory pattern.

I prefer Mockito's approach.

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It’s definitely a bit annoying and verbose in Java but I think creating an interface to support testing is a net positive. That interface is the specification of what that concrete class requires it’s dependencies to do.

I think all the dependencies of a class should define behaviour not implementation so it’s not tightly coupled and can be modified in the future. If you have a class that injects LookUpService, why not put an interface LookUpper in front of it? It’s a layer of indirection but we have IDEs now and reading the interface should be easier or at least provide context.

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