No book recommendations, sorry.
After reading your post, mainly I wonder did the tester know he was 4? I know she must have 'known' in the sense it was on her paperwork...but did she get it?
These sound totally like things my kids would and have done. For an 'extreme' example, we have a friend with a daughter who, when 3, "thought" she was a puppy for almost a year (not all the time, but a lot of the time)!
The parents went with it, even having a puppy birthday party when she turned 4. There were times they wished she would act 'normal', but they knew she was just having fun and learning about people, frankly.
