The second Portal 2 DLC titled Perpetual Testing Initiative will be available from the 8th May for PC and Mac.
As we've previously reported, this DLC will allow players to "easily create, share and play Portal 2 puzzles. The Initiative comes with a simplified puzzle maker that allows the creation of mind-bending puzzles without ever leaving the game."
The puzzle maker can directly publish maps to the Steam Workshop where users can browse, vote on, and select to play them. Selected puzzles will automatically be downloaded and installed inside Portal 2.
Remember the "Perpetual Testing Initiative" trailer will be aired today on GTTV.
UPDATE: Thanks to user Motanum, after contacting David Sawyer from Valve (who has been co-ordinating the Puzzle Creator internal beta), he has confirmed there is "no co-op mode in the initial release".
David Sawyer has revealed that puzzle creator created maps can be exported into Hammer for additional polishing. He has also revealed that hammer made maps alone can be submitted to the Steam Workshop.