Thanks Adric for your answer!
Well, I thought it was obvious what I wanted to test about enrollment duration, but I realized it was not: nerf me .
Ok, the thing I need to test is the expiration. I need to make sure students with an expired enrollment cannot access the course again. I know it may seem silly, but I did test it with a new course with an enrollment duration of 1 day, then enrolled myself as a teacher and a test student user... Now, I didn't want to wait a whole day, so I simply tried changing my sandbox server's date, and tried logging into my test course with my student user; alas, I could access the course . And that's why I came here to post a question about the "best way" to test enrollment duration (and should have added "and expiration" ).