I'm certain a fair number of the people here have done proper, controlled VO2max tests, and some of you may have tried the Cooper test as well.

If you have, how well did the two agree?

I haven't done a Cooper test myself yet, nor have I done any more serious test. However, I entered my time from my best 10 km run, which was just over 47 min (but a bit hilly), yielding 2500 m in 12 minutes. That gives me a VO2max of around 45 ml/kg, which isn't very good, but probably about average.

I'm fairly certain that I could run around 3000 m if I only did the 3 km and was properly warmed up before. That would mean 56 ml/kg, which is better but far from great.

The question is, is the test even close to real-world values, or is its predictive ability similar to the silly 220-age formula for MHR? The fact that it doesn't take body weight into account, while still giving a result that is clearly weight dependent, seems fishy to me...