Teachers hear all kinds of excuses. Like this one -
"You cannot hold me responsible for knowing the material on this test, as I was sleeping during all of your lectures. As you did not wake me up, I assumed that you sympathized with my tiredness and were excusing me from the information being covered. Not needing to know the information, I assumed that I would not have to take a test on it. You might have made some kind of mistake in handing me this test, since I don't have to take it, so I am just writing this to remind you."