It’s a tougher decision this year, now that students, especially seniors, have to register for the tests several months earlier than in the past. In previous years if a senior applied and was accepted ED (or RA), he/she would be able to check that college’s policy before signing up and paying the fees. All you can do going forward is review the polcies of the colleges to which you’re applying and make an educated guess based on your research. If you can afford the fees, I would err on the side of taking the exams.