@cored I would probably let mutant guide you on what you need to test.

One annoying thing is that you will probably need to assert the specific warning message. It's one of the few drawbacks to mutation testing. I suppose when we get the ability to filter out some mutations we can eliminate the need for this.

In this specific case you can assert that the message was sent to `Devtools.notify`, or you can have an object which accumulates notification messages and assert that it includes the message you expect.