Welcome to the club, read and watch folks' experiences and you'll probably see a lot of parallels with how you've acted in the past and learn from the lessons of how to cope with it.. there's no single thing that helps everyone (I remain of the opinion that ADHD is an over broad grouping that's actually a few similar specific neurodivergences stuck together because we still understand it really poorly).
There are tests? When I wanted to see if ADHD medications would help me, I just told my psychiatrist and he prescribed them. (They help me sleep less and lose weight, but they don't have the intended effects for me.)
Probably depends on state or whatever what requirements are.
They had me do a test using a VR headset, and I was like "Oh this will be fun!"
No, it wasn't. I had to stare at a VR aquarium and press a button based on instructions for 20 minutes like
"If you see a clown fish, then a blue fish, press the button" or
"If you hear me say Sturgeon, or you see a clown fish, press the button"
"Press the button if you hear the name of any fish that isn't a clown fish, or see any fish that isn't a sturgeon"
Apparently I did VERY poorly on instruction switching, with it taking several minutes between tasks for me to get the instructions down where they like bleed together. Also like little kids would walk in front of me, or a phone would ring, or TVS would flash.
I lose weight on them too, but just started recently. My psych asked me to grab a family member and do the Diva 5 test on my own and report back the results.