it gives the best avenue for a student to demonstrate knowledge.

I can't remember ever taking a test like that. These ones I've taken involve identifying specific answers to particular questions and following particular procedures for producing specific answers. I wasn't demonstrating my knowledge of anything except my test-taking skills.

Now, I have been told that there was a time when teachers discussed the subject matter with students during class, and then altered their methods and subjects to accommodate what the students appeared to understand, and what they seemed to need to understand. I've rarely seen anything like this myself, but this sounds like a far more sensible system of assessment and adjustment than testing to me.

I've even been told that, at one time, principals, department heads, and deans used to sit in on classes to see what was going on and evaluate the quality of the instruction. Again, I've rarely seen this happen, but it sounds like a fairly clever way for administrators to make assessments of and adjustments to the teaching in a school.

Teachers have thought this for a very long time,

The kind of testing we're talking about is very recent.

testing itself can be a learning experience.

Of course it can. It can help people learn how to take tests.

I'm in education

If it's not an intrusion, could you tell me what you do in education?