I dunno but here is a good test with lots of locations to select: http://www.azurespeed.com/
Latency will always be significantly higher than ground based Internet with lowest possible real world of around 600-650ms.
If you're referring to latency, Testmy does show it to you after you run a test. It's at the top, above "Results." There may be other places...I haven't looked, though.
Why is the single most important issue users have with satellite internet not tested by testmy.net?
Maybe because it's built right in to the modem connectivity test, but that only covers between the modem and gateway. If you wanted to check on a site overseas, you could always use the ping command from a Linux terminal.
I don't know if I really trust testmy.net that much, since it always shows about 50% more than the Hughes speed test on my system.
As well as what's already been mentioned, you can run a ping test on your computer, which will give you the latency to the server you choose, which in the example below is Google's.