I agree that having a unit test creates no real problem with regards to coupling. Providing a dependency really just makes the existing “hidden” coupling more visible.

But what do you do when you mock if not “create another object of the same type as Dependency”? The object/type is created at runtime, of course, but still, it is precisely what you do.

However, to test ClassUnderTest in isolation from an internally instantiated Dependency, it’s not necessary to “create another object of the same type as Dependency”. You can instead simply mock the Dependency class, allowing the test to specify the behavior that ClassUnderTest will see from that internal Dependency instance.

So, the (unit) test for ClassUnderTest will only need to reflect the simple-object and simple-data-parameter forms of coupling on Dependency, not any semantic coupling. That is, the unit test will have no knowledge about the “inner workings” of the Dependency.