When I interview front-end devs, I still focus on core fundamentals and I want to see if they can build simple interactions and layouts in HTML, CSS, and simple

When I interview front-end devs, I still focus on core fundamentals and I want to see if they can build simple interactions and layouts in HTML, CSS, and simple JS via jsfiddle. My assumption is that if they can do vanilla well enough, having them do React is easy enough. The reverse is often not the case.