Unit tests first feedback is to be able to easily write a unit test

I have this idea, the first feedback of a successful unit test, is not upon being green on running, it is on being able to write it easily.

A unit test that is being written and is making it difficult, most probably is a sign of code that needs refactoring.

A class that is decoupled, cohesive, short is likely a class that can be covered by unit tests with little effort.