Testing speed is the time in a 10, 20, 30, or 40 meter or yard sprint. Game speed is a cousin of testing speed. Game speed is the speed you can transfer from testing into the actual game or match.
I have been fascinated reading the comments on Super Bowl MVP, Cooper Kupp. The pundits are marveling at what he can do, and yet he can only run 4.63 for forty yards. To me it is not mysterious, he has game speed, he can adapt his speed to the game. He can, decelerate, stop if necessary, and reaccelerate more efficiently. I read a comment from him that said that is what he works on each offseason. Powerful message here – you can chase testing speed times and not be a better player unless you can transfer that speed to the game. Work on planting and cutting, decelerating, and reaccelerating.