Simple - to prove to yourself that you are getting better, and to give you FACT based information that you can discuss with your coaches.
We believe in improvement programmes that are based on fact - you often hear people say that they are swinging the club better than they ever have before - but are they hitting more fairways, or hitting more greens in regulation - in most cases they wouldn't have a clue.
Competitive golf is a results based business - it's played on a course against fellow competitors - to hear some players talk about their swings you'd think it was played on a catwalk.
Whatever the form of competitive golf you are playing, you keep score - you mark a card in stroke play and you know whether you're up or down in match play - so wouldn't it be the best preparation of all to keep score when you're practicing too ?
There is absolutely no end to the ways in which you can test yourself, but the left hand links are intended to give you a few ideas - we've used all of these in County Coaching.
The most important thing is to keep doing the tests, record your scores, and hopefully see an improvement over time.
If you aren't able to improve just by doing the tests, then that is the best possible sign that it might be worth seeking some advice from one of your coaches - and when you've taken and applied the advice of your coach, re-doing the test is the best possible feedback you can have as to whether the advice of the coach works.