I would echo what most people are saying and strongly advice against a written test.
If was a taking such a course I would want to end the class with a fully functional prototype that addresses all major areas of game development in the engine.
One suggestion would be to work on a single prototype during the semester. Start with a simple template, like the thirdperson template, and as students learn about the different topics they add new functionality to their game. So, once they learn about animations, their assignment is to add X number of animations to their characters. Once they learn about materials, their assignment is to make X number of materials with specific properties, etc
At the end, their prototype will have custom meshes, animations, materials, BP and C++ interactions, and even cutscenes!
You can grade it on the efficiency of code / BPs and creativity. Maybe you ask them to create a specific system and see how they solve the problem?
Just some ideas