My students already know what to expect for assessments because I make it a point to tell them in advance, so when they come in for this test, they know they will be working individually. I put the Complex Assessment on their desks face down and they know they may begin as soon as the bell rings. I also post a reminder on the board that multiple choice does not mean "multiple guess" and that I expect them to show their work for each problem. My video explains why I chose a multiple choice testing format for this assessment.
While my students are working on the exam, I walk around offering encouragement and redirection as needed. (MP1) I remind them when there are only five minutes left so they have time to wrap up whatever problem they're on. I discuss in my narrative a bit about why I chose to use a standardized test format for this exam. If any students finish early I encourage them to double check their work, then offer them extra credit for creating one or more problems that I could use for next year's class!