Online collaborative testing is an approach to assessment that emphasizes technology-mediated learning through interaction with peers. As the COVID-19 pandemic prompted exponential growth in online teamwork, skills for online collaborative problem-solving have become essential for today's graduates. As such, online collaborative testing can play a crucial role in supporting students to develop these skills. In this paper, we report on how an online collaborative test was implemented in a large first-year undergraduate course. We begin with a review of the literature on online collaborative testing. We then describe how the instructional team designed and administered a synchronous online collaborative midterm exam in which groups worked together to analyze a complex case scenario. Finally, we conclude with a reflection on the strengths and limitations of our approach and opportunities for future design.