[jd]

Tests are supposed to measure understanding of the subject material.

Therefore tests should be open book iff open book tests are better at measuring understanding than closed book tests.

Are open tests better? I remember from my university days that you can simply look at questions in the book that look sort of similar to the question on the test and apply the necessary substitutions. With open book tests it's remarkably easy to create an answer that looks intelligent about a subject you don't understand at all. With closed book tests this isn't so easy.

Even trivia questions can reveal fundamental gaps in people's understanding. For instance, if a student answers that dinosaurs existed 3000 years ago they must think within a frame of reference where 3000 years is a plausible answer (so no understanding of evolution). So it's a question that is easy to ask, easy to grade, objective, and one that can function as a great litmus test. When all tests are open book you can't ask these questions anymore.

So I'm pretty skeptical about the claim that open book tests are better, period.

As for the argument that people can look things up in books after they graduate, I don't buy that at all. The logical next step would then be to also allow students to ask questions on web forums during exams. Copy question to forum. Get coffee. Copy answer to test paper. After all, when the students get a professional job they may also consult web forums to get their work done.