About games' performance and gpus

[ntg]

I always see that when a new game comes out there is a raft of issues with gfx performance that take a number of driver updates to sort out.

So I've been wondering, how do the game developers test the games before release to make sure they work as designed if these drivers are unavailable? I may have got the process wrong I suppose but I'd be interested to find out how the whole testing for gpu's work.

 

[ntg]

I think I didn't phrase my question right, when game developers design and develop a game, how do they test their graphic engines/results?

Obviously they can't be testing it in the current line of gpu's or they would know they don't perform adequately (so then, how do you know how it's supposed to perform?)