If you are being trained to dive solo, how can an assessor be in the water, 'cos then they are your buddy...
I suppose it could be done on a process of elimination: "Go for a dive, if you come back you've passed".
I know divers who would do this course and then disobey all the rules and cause problems for themselves and the poor sods who have to look for the body.
Only you know when you are ready to solo dive, but you need to be honest with yourself.