I remember a teacher once told me you learn from tests. I found that to be true, in my own education. I learned the flaw in my thinking and the imperative to correct my error by study. Is that not true with testing today?
Indeed, testing is one of the many ways to improve learning. It is also a tool the educator can use to determine areas where re-teaching can improve student understanding and performance.
By my junior year in high school, I loved tests. I always wanted to see how well I did against the teacher’s standard. Because my school had full semester exams, my goal on the final exam was to beat my average score on all of the tests from the semester. Usually I had to relearn what I missed. So, yes, I did learn from the tests.