The mobile app ecosystem continues to rapidly grow in importance as an increasing proportion of our daily computing needs shift away from desktop machines in favor of mobile devices. However, mobile apps must cope with extremely diverse operating conditions due to factors like device fragmentation, wireless network heterogeneity and varied user behavior. App developers and distributors (i.e., operators of app marketplaces) lack testing tools that can effectively account for such diversity and, as a result, app failures and performance bugs (e.g., excessive energy consumption) are commonly found in mobile apps today. Towards addressing this challenge to mobile app development, we have developed key techniques for scalable automated mobile app testing within two prototype app testing services – VanarSena and Contextual Virtualizer. In this paper, we describe SMASH – our vision for a single unified cloud-based mobile app testing service that will combine the strengths of the VanarSena and Contextual Virtualizer systems towards solving the complexities presently faced by testers of mobile apps.