Automatic renewal after paying with a coupon

I am testing my site as a new member. When I pay for a monthly subscription ($10) with a coupon worth $10. On the subscriptions page it says my monthly membership is automatically set to renew. What will happen when the month is up? I have set up email reminders, but I was able to sign up without authenticating my email so I can;t rely on this. I just want it to go smoothly.