From the moment you are born, you are tested by the doctor or nurse to make sure all functions are a go. Then your doctor has you perform milestone testing during each developmental period. School begins and your teacher tests your performance in subject matters and doctors test your biological functions.
Testing, testing and more testing. That is what life is about. So if you are serious about fitness, training, endurance sports, etc., you need to track progress, ability and set training zones through proper testing.