The Perpetual Test Initiative is a level sharing, playing and editing service for the game Portal 2. It was developed by Valve and announced on 8 May 2012. It is free for everyone who bought Portal 2, and ties directly into the game. Players can create levels and play these. The levels can also be shared with other players online. The level editor provides a simple interface, where you can edit levels and test them.
 Story line
The Perpetual Testing Initiative storyline is that Cave Johnson of Earth One (our dimension) wants to save money, so he makes the employees of Aperture make many plans for test levels. Instead of building them in his own dimention, he sends the plans to the Aperture Science Corporations of other dimensions, and they build the test levels there. Afterwards, test subjects from Earth One is send to these dimentions to test the levels.
The test subjects you play as in the game have the a apperance of the humanoid figures in the trailers for the games.