I think apathy is part of the disease and I experience it with my mother. Not wanting to take the test can be a self preservation thing too, it's humiliating to do poorly.
Some of the things we've had better luck with include doing new and novel things like going to a museum which is stimulating, I bought a 70's music disc which she sings to when we are in the car. I make everything fun and call it car karaoke! (and actually it is fun for me as a caregiver too). I have her help me cook.
Basically try to do things that stimulate the brain without her thinking it's work. I have also had to accept that there are some things I can't influence her to do.
Caregiving can be hard. I am in a support group that has been really helpful for me. You may want to look into a local group. The one I attend is via zoom.