  Android Apps are frequently updated, every couple of weeks, to keep up with
changing user, hardware and business demands. Correctness of App updates is
checked through extensive testing. Recent research has proposed tools for
automated GUI event generation in Android Apps. These techniques, however, are
not efficient at checking App updates as the generated GUI events do not
prioritise updates, and instead explore other App behaviours.
  We address this need in this paper with CAT (Change-focused Android GUI
Testing). For App updates, at the source code or GUI level, CAT performs change
impact analysis to identify GUI elements affected by the update. CAT then
generates length-3 GUI event sequences to interact with these GUI elements. Our
empirical evaluations using 21 publicly available open source Android Apps
demonstrated that CAT is able to automatically identify GUI elements affected
by App updates, generate and execute length-3 GUI event sequences focusing on
change-affected GUI elements. Comparison with two popular GUI event generation
tools, DroidBot and DroidMate, revealed that CAT was more effective at
interacting with the change-affected GUI elements. Finally, CAT was able to
detect previously unknown change-related bugs in two Apps.
