The entire profession of medicine is obsessed with tests. This is unlike most other professions, which have the common sense of realizing that after an individual makes a certain amount of progress in the field, the job becomes less about bullshit basic knowledge and more about specialized knowledge and people skills. It is true that most professions have qualifying exams of some sort, such as the bar examination for lawyers. However, only medicine forces their practitioners to continually retake exams for the entire working life of a given person, even years after the person has received their medical degree. (As you might expect, masochists tend to do extremely well in this system.)
This process of continuous testing starts with the SAT in high school and continues with the MCAT in college. Many students freak out over these two exams, but in reality, these tests are jokes compared to what you'll have to deal with in medical school and beyond. During the first year of medical school, you can expect to have a quiz or exam every single week. (If you are in a systems-based teaching school, you can also expect to have anatomy lab practicals that coincide with the final exam for each sequence.) Thankfully, second year is a little less vicious in terms of exam frequency. At the end of the second year, all medical students are required to take a massive exam called the USMLE Step 1, which is a comprehensive test of the entirety of the previous two years. The USMLE Step 2 and Step 3 come later on, as well as national shelf exams all through the third and fourth years. However, don't think that the testing stops once you graduate from medical school; board recertification exams must be retaken every seven to ten years!
Ostensibly, this incessant testing occurs for the sake of patient safety. If you force people to refresh their knowledge base in order to pass a recertification exam, you might expect them take better care of their patients by drawing upon that knowledge base later on. The only problem with this sort of thinking is that seven to ten years is more than enough time in which to forget all the stupid minutia that you get tested on. The real test of whether or not a doctor is competent is whether or not they do a good job of managing their patients illnesses on a day-to-day basis, including taking it upon themselves to keep up with emerging trends in medicine. One would imagine that such a doctor would also be able to pass a board certification exam, but apparently it is too much to ask to have the exams be a replica of what doctors actually do on a daily basis. It makes much more sense to ask them to partake in an unnatural, non-intuitive process that tests them on knowledge that is marginally relevant to their ability as a clinician.
If you are considering going into medicine, you should come to terms with the fact that the best years of your life will be spent memorizing and regurgitating vast quantities of information (unless you decide to take some time off before going into medical school). You will basically be a glorified parrot, and your position could be better filled by any kind of PDA. The first point is even more true if you are female, as the longer you wait to have children, the more your uterus will shrink down to nothingness.