Writing a good exam is a lot like writing a good poem - it has to be full enough of stuff to make people think, and not so all-over-the-place that it becomes a fruitless exercise in guessing at meaning. I wrote, deleted, and re-wrote the same test question about six times before I figured out how I needed to phrase them so that I could tell whether the students actually understood the reading or were just lucky guessers.
I have succeeded.
I am now essentially done with two of eight exams, though I still need to create rubrics for them, and I have a third one formulated in my head that I need to organize on paper. By the end of today, I hope to have another exam fairly well completed.
Some time this weekend I'll be getting together with a colleague to help her with some exam writing for her classes.