The goal of this question is not to make sure the programmer knows your programming language. As long as there is no near-term critical deadline, knowing your language doesn’t matter. What matters is that the programmer knows more than one.
Does your candidate have the inner attributes needed to grow as a developer and face new challenges? Key questions can help you find out
https://mindmatters.ai/2020/02/what-to-ask-a-programmer-in-a-job-interview/
