I hereby absolve you of one piece of your async testing stress.

When you are testing "eventually X will be true," you can poll.

You do not have to create elaborate callback schemes.

You do not have to inject mocks that hide XCTestExpectations.

You do not have setup an AsyncStream or a Notification.

There is nothing wrong with asserting that something will eventually be true. It is exactly what you mean.

And in a unit test, there is nothing wrong with polling for that.