This simple test involves getting a shotgun and having your left leg blown off. If you didn't mind that much and are alive in 6 hours you pass the test and you have conclusive proof you are a zombie.
The test can be used on siblings and friends if you suspect at all that they may indeed be the walking dead.
This test does not make you very popular with the test subject, but hey, at least you know for sure!
"thanks to the zombie check i havent been attacked by a real zombie for months, now i can be certain!"