I've installed GNU Ring on my system, but, frankly, none of my friends use it (none that I know of anyway), so I don't have anyone to call. I'm planning to invite someone to call me up on Ring, but I want to test it first. If you use (yes, I'll say it!) Skype, there's a "Call Testing Service" which you can try. Is there something similar on Ring? Or perhaps even some automated service with a different goal, that's accessible via Ring instead of people I would be bothering with a phone call?
Bonus points for a way to test the SIP functionality as well.
PS: I'm using Linux Mint 18.1 in case it matters at all.