Hi,
Don't worry too much about it. If you have gone through the booklet a couple of times and "understand" what it is talking about, I would be surprised if anyone will fail. I'm July applicant BTW.
The test itself was pretty easy and straight forward, got 20/20. I don't thing they want to fail anyone. Off course if you go without any preparation or have difficulty reading/understanding English/French, then that would be an entirely another matter, and, there are resources available for such scenarios.
Do remember important dates/years/importance related to topics like Canada Day (Duh!!), Magna Carta, British North America Act, Vimy day, D-Day, USA war, Women being allowed first to vote, acts for end of slavery, battle of Abraham, democracy first etc. to name a few.
The questions were structured in a sense that you can make an intelligent guess as well, and if you have read the booklet a couple of times it will ring a bell for sure.
For example, there was a question about why a structure was built and they mentioned the year in the question (when it was built) and the options were far apart in years. So if you forgot the exact reason you can still pick the closet thing that happened matching with the year mentioned in the question. If they
underline something in question, pay attention.
There were not many questions specific to precise dates, and again if you miss few it should not be a big issue. Remember you have option to mess up 5 outta 20.
Also make sure you remember names of folks IN THE BOOKLET like famous Hockey player, gold medalist mentioned in the booklet, famous art individual/s, scientists, achievements. Again 1 or 2 questions like that, and if you miss out it won't be a big deal.
I split the booklet into different chapters, used highlighters, underlined important stuff to quickly review, later. I studied 2-3 days for few hours and went through the booklet 2 times. Did some online tests like Richmond Library and Apna Toronto, good for practice though booklet is a must.
Relax and just read the booklet. I enjoyed the booklet and learned a lot about Canada's history.
Again I can assure you if you read the booklet and understand what it is talking about, you will PASS. I'm not sure if we are allowed to share specifics of what was in the test, so I will refrain from posting any specific Q&A
TLDR:Read the Discovery Canada, and you will pass.
Hope this helps.