My favorite front end interview did this exact thing. The interview started with an issue taken straight from the Preact GitHub codebase. The interviewer provided the issue text and the commit right before it was fixed to pull down onto my machine. I had an hour to figure out how to build and reproduce the issue, Take in the high level structure of the code base, figure out how to drill down in a debugger to find where the issue itself was occurring, then propose a fix for it. Took the whole hour but was both extremely satisfying for me, and I imagine very insightful for the interviewer.