"What you do is test the extreme cases. In Deus Ex, I made people play through without ever using a weapon. I made them play through and kill absolutely everything that moved. Or get through the game without ever using a skill, or an augmentation. If you do that, you can be pretty certain that anything in the middle is gonna work. Publishers hate that. It's really scary, but people are going to figure out how to do things that are impossible. In Deus Ex, we had so many people figuring out how to get outside of the gameworld that we had to put crates and ladders outside the maps so they could get back in." - Warren Spector

Remember, Epic Mickey 2 is going to have multiple decisions that actually matter for gameplay. You can do things that can't be undone. You can play however you want and tackle things your own way. As you can see, that kind of freedom can be a nightmare for bug-testers!