Not really a unit test

Huh, ignore the above particulars since (as any school boy should know), 32767 is a long way
short of 2^31

However unfortunately the birthday paradox actually doesn't help you in this case because the
"random" factor isn't - you will likely run your unit test on a single machine where PID (the
main source of "entropy" left after the disastrous Debian patch) is happily incrementing
slowly for each key generator process you run, so you won't get a collision until your PID
actually wraps.