I'm wondering how wizard identification works. In my story, a
bartender only serves wizards of age, but how does he know? Do
they carry I.D. around like we do? Or is there a magical test
that the bartender can easily do to check their age?  If there
is a test, how does it work? Does it give age? Name? Address?
Can it be tricked (like Fred and George tried to trick the
Goblet)? Does the person have to willingly submit to the test or
can anyone walk up and find who you are?  I have lots of
questions! Thanks so much for any help!