Sometimes your react component may need to do some cleanup work in the return value from useEffect or useLayoutEffect, or the componentWillUnmount lifecycle method for class components. Luckily for us, as far as React Testing Library is concerned, whichever of those you use is an implementation detail, so your test looks exactly the same regardless of how you implement it. Check out how you can test that simply with React Testing Library and a <Countdown /> component.


Test Unmounting a React Component with React Testing Library