I have a friend who lives in Whitehorse, and he flew down to Vancouver to take his test and oath on the same day. His notification letter clearly indicated that it was a combined invitation for both. It offered him a choice of dates, indicated that taking the oath was of course dependant on him passing the test, and also that it was a limited opportunity so he needed to respond quickly.
If you have just received a test invite and there is no mention of the oath, then you should assume that it will not be the day after and that you will need to wait for a separate invitation to your oath at a later date.