A "pop quiz" is a surprise test that teachers give to students without warning. It tests their knowledge on a subject, and they have to answer it on the spot without any prior preparation. Full definition
Have a boss who likes to give pop quizzes after he talks for two hours? (health.com)
For some, the words first «assessment» bring up memories of pop quizzes or exams. (invigophysio.com)
The bulk of the course consisted of short videos of the instructor, pop quizzes after the videos, and assessments at the end of each of the four modules. (slaw.ca)