You can go and ask at the service-Ontario centre and they should be able to tell you if your car needs emission test based on the year you bought your car. For example if you bought your car on 2005, then this year you would need to do the emission test for your car. Usually the time to renew your car sticker is the time that coincides with your birthday date.
The other option is to go to the service Ontario website and there is this link: http://www.downloads.ene.gov.on.ca/files/driveclean/onesite/en/ldv_when.asp
Simply enter your postal code, model year of car and license plate sticker expiry date. It will tell you if your car needs emission test.