Ah. I just provide all my answers in an obscure language they won't know, but has lots of "nerd-cred", so they feel uncomfortable questioning it. Like OCaml, Erlang, or Haskell.

Then in the rare case they question it, which usually goes something like, "Can you do it in Java? We don't use whatever language it is you're using there." I respond with, "Oh, will I be spending a lot of time at this job coming up on-the-fly with somebody's PhD thesis from the 60's?" To which the answer is always, "No." Which finally ends the conversation with me saying, "Well then you asked me to solve an irrelevant problem, so I'm happily providing you an irrelevant answer."

I have a fair bit of contempt for the pitiful state of technical hiring and assessment process out there. I think that comes mostly from my opinion that hiring is probably the most important thing any company or manager does, and that if any one of these companies/interviewers put even 10% the amount of effort into learning about educational/occupational assessment, psychology, and neurology that they do into obsessing over the dubious idiosyncrasies of the latest framework-rehash-of-the-month, then these terrible interview practices wouldn't endure very long, and we'd all be spared the indignity of the farce on both sides.