Passive vs Active Voice: The Zombie Test

“Is this passive voice?”

I absolutely dread this question in a critique session.  My grammar isn’t horrible but I am no grammar Nazi.  Is it passive voice?  Or did you just use a helping verb?  Your guess is as good as mine.  Active verbs are best.  That’s all I know.

Or at least that’s all I knew until I learned about the Zombie Test.

. . . by zombies.  All you need to know to detect, and get rid of, passive voice.