  Graphical User Interface (GUI) has become one of the most significant parts
of mobile applications (apps). It is a direct bridge between mobile apps and
end users, which directly affects the end user's experience. Neglecting GUI
quality can undermine the value and effectiveness of the entire mobile app
solution. Significant research efforts have been devoted to GUI testing, one
effective method to ensure mobile app quality. By conducting rigorous GUI
testing, developers can ensure that the visual and interactive elements of the
mobile apps not only meet functional requirements but also provide a seamless
and user-friendly experience. However, traditional solutions, relying on the
source code or layout files, have met challenges in both effectiveness and
efficiency due to the gap between what is obtained and what app GUI actually
presents. Vision-based mobile app GUI testing approaches emerged with the
development of computer vision technologies and have achieved promising
progress. In this survey paper, we provide a comprehensive investigation of the
state-of-the-art techniques on 226 papers, among which 78 are vision-based
studies. This survey covers different topics of GUI testing, like GUI test
generation, GUI test record & replay, GUI testing framework, etc. Specifically,
the research emphasis of this survey is placed mostly on how vision-based
techniques outperform traditional solutions and have gradually taken a vital
place in the GUI testing field. Based on the investigation of existing studies,
we outline the challenges and opportunities of (vision-based) mobile app GUI
testing and propose promising research directions with the combination of
emerging techniques.
