We have tested it.
We have the Moon, Earth, Mars, and probably have calculated the gravity of the sun.
Oh yeah- forgot about the moon. Although we haven't been there very often, and I don't know if we did tests with gravity while we were there. I could be wrong though. As for mars, it's nearly the same size and wouldn't be very helpful.
Not sure how we could do the sun though, -actually I have no idea, lol
Just because we can't get there, YET does not mean someone or something else is not there waiting. Once we reach warp speed we can find out what.
I'm just saying I doubt there's anything on that planet. That's just my opinion