> Ask yourself the question "What tends to get mocked?"

Answer: every collaborator of the object under test, so that only the tested object is actually having its implementation exercised. All other objects that it needs to talk to — database connections, network sockets, or whatever — are replaced with mocks, and the test subject’s interactions with those mocks are verified, so that a) we have confidence that the tested object is interacting with its collaborators in the expected way, and b) the test itself doesn’t depend at all on the actual behaviour of those collaborators’ implementations, which behaviour should be explicitly exercised elsewhere.

That’s the opposite of coupling. I don’t understand where your answer comes from or what it means.