In order to do this glitch, you must activate both infinite health and portal placement anywhere cheats. infinite health cheat code is LB d-pad up RB d-pad up LB LB d-pad up RB RB d-pad up. portals anywhere code is YABABYYA d-pad left d-pad right. alright, first, fire a BLUE portal at the first camera (the closest one to the entrance) and when the orange portal opens up, you should fall out of that chamber. i havn't tried this on any other test chamber so i think it only works on chamber 4. have fun :-)