A ping test is a way of checking for glitches that could slow down Internet communication. Skype's options menu includes the ability to run a ping test covering you and another specified user, though it uses a different terminology.
Ping Explained
A ping test does not measure how quickly information travels back and forth over an Internet connection. Instead it measures how quickly that connection allows a computer to respond to a request for data and begin transmitting it. A long ping time can introduce noticeable delays into an Internet voice or video conversation.
Pinging on Skype
You can only ping somebody when both you and they are logged into Skype. To ping, click the person's name, click the call quality information button (an icon of five red vertical lines of increasing size), click the "Connection" tab and then click "Test now." After a brief delay you'll see a message telling you if the connection between you is adequate to make a call -- in other words, whether the ping time is short enough or too long.