I don't think it's unfair at all, but your comment made me rethink something that may be relevant. Quirrel set a surprise exam, and it was surprisingly easy and everyone (except Hermione) passed. I think probably the worst thing that you can do in the face of a surprise exam is not attempt to answer, and maybe that's part of the lesson EY is trying to convey here :-)

I also note that Quirrel failed Hermione in the knowledge that he would be resurrecting her, and this is either very mean, or a very good lesson for resurrected Hermione, or both.