The play-in/play-out approach suggests a new paradigm for system development using scenario-based requirements. It allows the user to develop a high level scenario-based model of the system and directly execute system behavior. The supporting tool, the Play-Engine has been used successfully in several projects and case-studies. As systems developed using this method grow in size and complexity, an important challenge is maintaining models that are well understood in terms of their behaviors and that satisfy the original intension of the system developers. Scenario-based methods are advantageous in early stages of system development since behaviors can be described in isolated fragments. A trade-off for this advantage, however, is that larger models comprising many separate scenarios can result in executable behavior that is difficult to understand and maintain. A methodology for facile testing of scenario-based requirements is needed. Here, we describe a methodology and supporting prototype implementation integrated into the PlayEngine for testing of scenario-based requirements. We have effectively applied the method for testing a complex model containing several hundred scenarios.