Testing for accuracy (general curiosity)

[Koji]

My curiosity got the better of me so I figured I'd ask a couple questions...

The one that's most on my mind is how do the devs check for accuracy when emulating a feature? Do they write a demo program of the function then run it on real hardware then compare it's results in emulation? Or do they find an existing game with said function and use some device to capture memory in real time on a PS2 to use as comparison?

I ask because I've always been curious about how developers tackle these issues... especially in the case of something as complex as a last gen gaming system.

[Bositman]

Sometimes yes devs have written actual code that runs on the PS2 and prints results for example. But mainly it is done via testing of beta testers and cross-checking with the ps2 (if not sure or the problem is not obvious)