At the
beginning of chapter eight "The Itch" you'll encounter a room with box/turret hybrids, a frustrated Wheatley, and a single pressure pad. Put a box on the pressure pad and continue to the lift, at the top of the elevator you'll be in test chamber 01 with the word "TEST" written in large letters on the wall. Its a simple chasm with a button that releases a cube and a pressure pad.
Get off the lift to make Wheatley start talking, then make sure that you
- DO NOT PRESS THE BUTTON
- DO NOT STAND ON THE PRESSURE PAD
Just stay in this room for about half a minute and you'll get the achievement.
For the visual people I've attached a link to a video guide made by "batou9secti0n" for the PC version of the game (which has the exact same achievements).
It shows the room in question to avoid any possible confusion. Full credit for the video guide goes to him, not me.
EDIT: updated link as original video was taken down