How can I verify what feedback the student sees? I guess when I switch to student role, I can do the test myself and can see my feedback. But I probably can't see the feedback other students got.
If you can, the best way to see exactly what students see is to make yourself a second user account, with a name like "Test Student", and add that account as a Student in your course. Then you can log in as that user, and see exactly what a student will see.