Responsive mobile web applications are quite challenging to test, especially if they require heavy interaction with the environment (e.g., through GPS-based location tracking and camera-based QR code acquisition and recognition) and among different users, as in the case of collaborative games support, where the app needs to support the real-time interaction of a large number of users. In this paper, we propose a case study of orchestrated crowdsourced testing of such a mobile web app, as an approach to face such challenges.