21st Century Standards and the Deeper Learning movement emphasize the ability to think critically and solve complex problems, to work well in teams, and to communicate effectively. While traditional classroom activities can meet these objectives, digital games and simulations provide unique affordances. When designed to incorporate formative assessment functions, games and simulations can capture detailed data on learners' performances and provide learners with immediate feedback. In spite of their strengths, barriers exist to practitioners' adoption of game-based and simulation-based formative assessments. Adoption can be slowed where product designs do not account for unique local requirements of classrooms and schools. The current work investigates reduction and removal of barriers to adoption of games and simulations among classroom instructors through use of the Integrated BEAR Design System (IBDS). The IBDS provides a design process that accounts for local requirements by engaging practitioners in principled design and development of game-based formative assessments. The paper summarizes the IBDS and a single case in which the IBDS was applied to design a game-based formative assessment for collaborative-problem solving, Little Fish Lagoon. The game is accompanied by a stand-alone chat system, Libra Text, that allows collaborating players to send text messages to each other while they use the game. Study participants were six instructors from six U.S. schools. The participating instructors planned for broad adoption of the multiplayer collaboration game in their local classroom settings. The authors illustrate their use of the IBDS with the participating instructors in order to co-develop formative assessments that fit their local needs using data collected from the Little Fish Lagoon educational game and the Libra Text chat tool. The benefits of the IBDS, its implications for learning designers, potential improvements, and needed future research are discussed. The paper is expected to be of interest to learning and assessment designers working with educational games and simulations, and others interested in barriers to adoption of new technologies in general.