Improved, re:  Regarding: https://bugzilla.mozilla.org/show_bug.cgi?id=1092375

That's just returning true or false, not throwing…
Wait.  Actually, that's just returning a function.  Did you want `oneOf(['nps', 'stars'])(which)`?
(That also doesn't work, because `thing is not a function`.
 If you use `choices_array.indexOf(thing)` instead, then it would return true or false, but still wouldn't throw.)