The teacher doesn't really care what the answer is, presumably the teacher could do the calculations without asking the student. The teacher wants the student to do the work. The student wants to get a good grade without doing the work. The importance of testing As we advance technologically, we depend on testing to keep us safe. New drugs have to go thru long expensive tedious trials.
Cars have to be crash-tested.
No we shouldn't, if only because someday a car or a drug might rely on software as part of a testing process. Or a moon mission, or your tax return. Computers are everywhere. We need to trust the people who make computers to have a high level of integrity. We want meaningful comparisons, and if a bit of software is slow or unreliable, we want to know before we bet our money or careers or safety on it.