Well for me the “test” was just my doctor pulling or the A.D.H.D.-A.D.D. checklist and asking me about my childhood, school (how I was in class and studying) how I was at work and private life.
It was similar to the online evaluations but longer.
She showed it to me, there were checkmarks in all but one for inattentive A.D.D. and nothing for hyperactivity.
That’s why it took till I was an adult to get myself tested, not sure when or if its changed, but when I was in grade school they only tested you if you were hyper, so because of that I have the wonderful emotional baggage of “you’re lazy, stupid, dumb, what did I do to deserve a child like you” and it still echoes in my head to this day.
Before I went to my doctor, I took every online test I could find, they all said to see a doctor, I even printed my results to show her (she just took my word for it, ugh what a waste of ink).
If you are unsure about the test, call wherever you will be going, and ask them for information and tell them your concerns.
Many of the things you said about, procrastination, waiting till crunch time for assignments, I’ve DONE that, it’s the adrenalin (stimulant) kicking in giving your brain what it needs to focus, the fight or flight response.
Also I think the more involved and elaborate tests are so they can observe you for physical traits while performing tasks (I remember reading it somewhere, but don’t quote me on it)
Good luck, hope it goes how you want it.