This is true. We use Elim students as testers as I used to work there as a teacher (don't hold that against me ). It's really important for the designers to see people playing and to see where people get stuck or which bits are too easy or where we need to have better clarity in the dialogue. We also do what we call "brute force testing" when, as well as looking at how the game play is going, we test the infrastructure for what happens when you get up to 100 people in the same place doing the same mission. The suggestions the testers make go straight to the designers and they are able to then see the changes when they play.