Fact that they even asked you to submit medicals is a really good sign. I think the interview is so that the visa officer can be 100% sure you are a student before issuing the visa as unfortunately some people may have "perfect" study permit applications but when interviewed in real life their case falls apart as it becomes apparent that they really just wanted to go and work in Canada. So if everything of yours is in order and true, then Im pretty sure you'll get the visa.