I think it probably is saying: don't write a "useEffect runs when its dependencies change", write a "User is redirected to their accounts page after loging in",

I think it probably is saying: don't write a "useEffect runs when its dependencies change", write a "User is redirected to their accounts page after loging in", and you are testing both your own code and the framework's routing / side effects handling / state tracking, etc. Integration tests for complex flows inadvertently tests your dependencies, which as you say is awesome for when you have to upgrade.