while (!dead) learn();
// a virtuous cycle
Asserting that something didn't happen is a test smell. There are an infinite number of things the test subject should not do. This code should not throw an exception. It should also not create a file. Nor should it make a sandwich, raise the Bat-Signal, or blow up Earth. These are all equally useless things to test for. It just doesn't give us any information to know what didn't happen.
That's not necessarily useless information. But we don't write code to not do things. We write code to do things. If we explicitly need to not do a thing, that is typically because we need to do something else a little later. That something else is the thing we should test for. Not always, but often. And I would argue that in clean code, it is almost always the case.
while (!dead) learn();