Great question! I give the same grade to each student in the group based on the final product. It's true that group work does not assess each individual's knowledge, but it offers the benefit of teaching them to work together. My students know that I am also grading each of them on their ability to collaborate with each other, so after a little bit of pushing they have group discussions on how to tackle problems rather than each member doing their own thing. Finally, my students tend to be extremely motivated since they want to be in my class, so I rarely see them foist all of the work off onto one person. Breakout is a major cumulative project, so I use it to give students the opportunity to engage in group programming and get a sense of accomplishment. I have plenty of other assignments I can use to assess a student's individual ability.