Yes, it's a hard question, but if you're grepping for skilled programmers you want a hard question. The point of these types of tests is not to minimise false n

Yes, it's a hard question, but if you're grepping for skilled programmers you want a hard question. The point of these types of tests is not to minimise false negatives, but eliminate false positives. (And besides, "I need to replicate this addition-based functionality but for multiplication" does not seem like such an Eureka moment to me. The main difficulty for me seems to lie in navigating a big codebase, and exposing a new function on the API -- the difficulty of which depends on how well modularised the codebase is.)