First off, exams like fizzbuzz, "find the bug", "what is the outcome of " and many others are a joke! Look up 'Griggs vs Duke Power Co.' Whether it is tech or some other field more often than not, tests like these give absolutely no indication as to how well or poorly the person will do the job. If you block a person from working at your place because they can't do fizzbuzz in 12:30. You my friend are a moron. Coding fast != Coding good...
In many situations tests during the interview process are a nefarious way to racially discriminate or gender discriminate or age discriminate without having to actually admit that is what you are doing.
In other situations tests many times are a very cheap way for a "senior" or "lead" to trap/trick a potential candidate so that they can protect their current job. Often a senior or lead is the one asked to make the test...
I once was asked "what is the command to partition and install a hard drive in a server?" -- My answer: Is that an everyday activity here? You need to use fdisk or gparted and/or other related commands. Then again is if it is a Windows server then there are another whole set of tools to use (ex, Partition Magick )."
Now on some days and with some candidates that will be a fine enough answer move on. However, if for whatever arbitrary thing that question could also be "interpreted" as incorrect to simply make sure a friend is hired instead, or uncle, or white person, or better dressing person or someone else that doesn't threaten your job.
Additionally, the only thing that you are testing with a question like above is whether or not the person has in recent memory partitioned a hard drive... which isn't really useful for anything.
I've turned down job openings too when they crack out these tests. If my 16 years of experience, linkedin recommendations, and open readable coding examples I share online are not enough to convince you that I can do the job. Sorry you got bigger problems than just an open position.