Testing Java Webproject

I'm in my third year of technical college, and have to do a project. So my Idea was to do a Java Webproject where the user have to do some programming exercises. Like a tutorial with exercises.

My Question is: How can i test the Input of the User, the result? JUnit? Could you give me some tips, how i can do such an project(like frameworks, how i can test the result).

I have tried to read the responses here.

Just to know how i can get a good start :)

Thanks in Advance