This flash game is pretty awesome. It's still in beta form and it's only being developed by one guy, but it looks like it'll be a highly addicting flash platformer that's pretty faithful to the original game.

If you want to help him do some debugging by playing through and checking for physics-based bugs, you can get on the forums and let him know and help him improve the game. In my own youth I somehow never managed to be an actual all-out game tester for anyone ever... that would have been a relatively great job, though, you'd think. More pocket change for playing games and discovering errors? Please.

(EDIT: I read that again and it looks sarcastic. I mean YES please. Really.)

Then again, some companies play test their games a lot more hardcore than others. Valve is one example. They play test the everloving crap out of their games, they get all their friends and family to test the games for years to notice trends and fix as many bugs and quirks conceivably possible in their games. This is hardly efficient but it sure makes for a limited amount of polished product in the end.

Anyway, go play the flash Mirror's Edge game and do some playtesting of your own.