Not so much debugging. Same create-react-app setup, but increment a counter on a button press. The solution is to add an event handler (which requires binding or an arrow function for the right context), and increment a state variable.

That and the debugging example are surprisingly effective at weeding out people who have "React" sprayed all over their resume but can't do one of the most common things.

We had one person who apparently had no fear of "3-1 pair programming with strangers" and instantly came up with the solution. She ended up taking a better offer though. Can't blame her. I wouldn't do as well as she did, and I wrote the damned thing.