Test of Might seems coded wrong

madwren

Test of Might says, ""When a creature you control deals damage to your opponent, your opponent takes an additional 8 damage."

My opponent's Samut had Test of Might out, and a Honored Hydra in play. Honored Hydra has no special abilities aside from Embalm. 

I cast Hour of Glory on the Hydra. After dealing damage to my opponent, Test of Might then did 8 damage to me. I confirmed it in Battle Log. This should not have happened, since Samut's creature did not deal damage to me in order to trigger it.