Wow, these guys are just so slow at everything. But shd feel good to know whats ahead of you atleast. Normally the interview is as a result of not living together physically for a while or less proof of relationship. Anyways a friend of mine who got interviewed said most of the questions were basics and mainly related to the file submitted. Thus;
When they met, how they met, how long, who introduced yall, hobbies and interests, also about the ceremonies be it wedding and reception, family & friends who know about yall and were present at the event etc.
I would suggest you study your file very well especially sector's where involves both of you to fill about your relationship. Another thing is to be really calm and honest during the interview cos at times the officer could be moody and might affect his decision. So be yourself and communicate well with him/her. You could also check out this thread
https://www.canadavisa.com/canada-immigration-discussion-board/threads/spousal-interview-questions.157678/ soo many questions there which might maybe freak you out so I think best to study your file.