When I did it there was no option in my area to just challenge the test, it was conducted in 4 (I think) classes and then the exam day. So 5 sessions in total (if I recall correctly).

Anyway, the first half of the classes was just going over the material covered in the book. The book is where all the information on the written portion of the exam comes from. From what I remember, the questions for the written portion are all multiple selection and they are all stupid simple. Just read through all the answers twice before selecting the right one. There were no trick questions and I think there was only one trivia sort of question. Something like "To what distance is a .22 LR lethal?" and even though it seems like a sort of trivia type question, the answer to that question and every other one is taken directly from material in the book. My instructor loaned books to us if we needed them, I don't know if that is standard practice for all instructors.

The second half of each class was dedicated to practical aspects of firearms. We were shown actual (deactivated) rifles and shotguns and took turns handling them and practicing the normal safety procedures. The standard sequence was this:
1)The instructor designates which direction is down range.
2)You select the action you want to learn more about.
3)The first thing you do after picking up the firearm is ensure that the muzzle is pointed down range.
4)Ensure the firearm is unloaded. Open the action and inspect the bore, then leave the action open while still keeping your muzzle pointed down range.
5)Read the barrel of the firearm to determine its caliber/gauge and the type of ammunition it is chambered in.
6)Select the correct ammunition from a pile by reading the bottom of the cartridge/shell.
7)Load the firearm while keeping the muzzle pointed down range and put the safety on after it is loaded.
8)Unload the firearm and leave the action open, then set it on the table with muzzle still pointed down range.
*Note* At no point does your finger ever go inside the trigger guard. Ever. At all. There is no time throughout the entire experience from starting to finishing the course that your finger enters a trigger guard.

Throughout the instructor may ask questions.Things like what is the model of the firearm, or what type of safety it has, or even what type of sights it has. The actual practical portion of the exam is entirely based on safety and no trivia about sights of model numbers will be tested (as far as I know).

It really isn't a difficult exam, I got 100% on both written and practical. Just make sure you are familiar with the 5 different actions, and if you get the opportunity to handle the test firearms beforehand then you should. The deactivated firearms we were shown in class were the same ones used in our exam, so if you have the option of class sessions then you should go to them.