  Mobile app development involves a unique set of challenges including device
fragmentation and rapidly evolving platforms, making testing a difficult task.
The design space for a comprehensive mobile testing strategy includes features,
inputs, potential contextual app states, and large combinations of devices and
underlying platforms. Therefore, automated testing is an essential activity of
the development process. However, current state of the art of automated testing
tools for mobile apps poses limitations that has driven a preference for manual
testing in practice. As of today, there is no comprehensive automated solution
for mobile testing that overcomes fundamental issues such as automated oracles,
history awareness in test cases, or automated evolution of test cases.
  In this perspective paper we survey the current state of the art in terms of
the frameworks, tools, and services available to developers to aid in mobile
testing, highlighting present shortcomings. Next, we provide commentary on
current key challenges that restrict the possibility of a comprehensive,
effective, and practical automated testing solution. Finally, we offer our
vision of a comprehensive mobile app testing framework, complete with research
agenda, that is succinctly summarized along three principles: Continuous,
Evolutionary and Large-scale (CEL).
