There are two exams -- one for Non-restricted and one for Restricted firearms. They are actually quite similar to one another and neither one is very difficult for someone who has experience with the appropriate types of firearms and has read up on the laws.  If you want to challenge the exam(s) you may want to obtain the book(s) first.

Both exams have two components -- a written, multiple choice part and a practical session in which you will be asked to show safe handling of several firearms and walk through several scenarios. There are 50 questions on the written portion, some of which are simple true/false and others offer multiple answers. You have to get 40 correct answers to pass.

Here's a link to some sample exams to help you decide whether to take the course(s) or simply challenge the exam(s). To help you prepare, you should go through the full exams on this site before challenging the test(s).

In the practical part, you will be asked to handle at least 3 different kinds of firearms, under different conditions. The examiner will never ask you to do anything unsafe, so passing or failing is entirely up to you. Every time you handle a firearm, you have to prove it safe, of course and marks will be deducted for missing the necessary steps. You lose two points every time you point the firearm in an unsafe direction, or put your finger inside the trigger guard when you are not supposed to, or attempt to load the incorrect (dummy) ammunition. You need to get 40 marks out of 50 on this portion to pass.

If you point a firearm at any human being (including the examiner!), you are done for the day. That's the only way to instantly fail the exam. The only exception to this rule is when doing a visual bore inspection on an open, proven firearm.

There's no time limit, but most people take about 15 minutes for each of the exam sections. After completing the exam(s) your paperwork will be forwarded to the Chief Firearms Office of Ontario where it will be processed and a duly certified copy will be returned to you in a few weeks. Attach this copy to your Firearms License application.