Forms is a straightforward, easy-to-use app, that also provides immediate feedback. I have used it to put together tests and surveys for students! It shows you students' data through bar graphs, pie charts, and gives you several options on how you want to review students' answers/work.
However, I have found one drawback to this program. Students must finish it all in one-go, or they lose all their work. In adidition, they are not able to go back and change their answers (when doing corrections).