Warn when users verify an invocation they also stubbed

[searls]

This is a super common error that we can detect and warn for. If you stub a particular invocation like fetch(42), then it means the subject needs that return value to do something else and the test's assertion should be about that something else. To also verify that fetch(42) was called ought to be redundant.

Is console.warn the best way to warn users in browsers & node? Should I throw an error but with a squelchWarnings config option?