As each student comes into the room, I have him/her draw a popsicle stick from my "kids-in-a-can" cup that has a stick with each students name on it. If they draw their own name or someone already teamed, I just keep that stick out and have them draw again. I remind them that if they can't agree on an answer, they may opt to each write and sign their own response, but that my expectation is that they will find collaboration the best way to work!
I distribute the Probability Unit Assessment and tell my students that they have the rest of this period to complete it. (MP1, MP2, MP4, MP6) While they are working I walk around offering encouragement and assistance as needed. Some teams will struggle with writing things out and for them I make the suggestion that they talk to each other quietly first and just jot down notes about what's being said, then rewrite those notes into complete sentences. I tell them when there are only five minutes left in class so they can finish up if they're not already done.
I know that team testing is not the easiest to administer or assess because as teachers we most often measure progress of individual students or classes. I've found that by the time this assessment is given I already have a pretty good idea about individual strengths and weaknesses. This is more about helping my students build their collaborative skills, something they will definitely need in the real world, as discussed in my video. If I have team lessons but assess individually it sends the message that when crunch time comes it's really not about working together and that's not what I want my students to learn.