Some teachers teach their students something brand new and turn around and have a test on it in the next few days!
Do you think that it's a good thing to do?
If not, ----is it bad???
I'm not a teacher, so please consider any advice I give in that context.
I think it depends on the test. There is nothing wrong with giving the students a quiz to see how well they have been paying attention.
It depends on whether the test is to check learning or to assess.