GLaDOS nodded. "Right, the Cooperative Testing Initiative." yes, she wanted to test it...but not like this. Not like she has a choice, though. As such, she doesn't bother speaking further after that. Instead, She merely frowns and follows Chell past the catwalks. As she walks, she doesn't say anything, just scowls.

However, that changes one they make it into the elevator. "These next tests we'll be facing are like nothing you've experienced before. I designed them in order to be done by two test subjects. Ergo, you and I must work together. Again."

She paused, before sighing. "However, that's not what you should be worried about. If you recall, I can't help you with tests. As in, if you're stuck on something, I can't give you the answer...directly at least. So don't mess up. Otherwise we're both dead."