I had one past psychologist give me an extremely long test during my first week with her. Maybe 500 questions. I suppose it could have been used for diagnosis assistance purposes, but I think she just wanted to know where I was at at that particular time, mood-wise and/or wanted to have a confirmed record in her files that supported the diagnosis I stated I had. There was no change to my diagnosis in the end. I do remember asking her if I could write notes next to my multiple choice answers since if you're not "currently manic" or "currently having sleep issues" that those are represented in some way. Truth is, sometimes such tests have poorly worded questions or ones that could form a misrepresentation.

I had a couple other psychologists who had mini tests I was to take every time I would see them. Just before the session while I waited in the waiting room. Again, I saw them more as helping them know how I was that day/week.

I've switched therapists often these past 15 years. I often brought copies of hospital records when starting with someone new. It is, indeed, frustrating when a new therapist or psychiatrist wants to start from scratch with diagnosis. I do know that sometimes diagnoses can change or be discovered, but after so many years it becomes less likely that it should.