Smartphone users have come to expect high-quality apps. This has increased the importance of software testing in mobile software development. Unfortunately, testing apps-particularly the GUI-can be very time-consuming. Exercising every user interface element and verifying transitions between different views of the app under test quickly becomes problematic. For example, execution of iOS GUI test suites using Apple's UI Automation framework can take an hour or more if the app's interface is complicated. The longer it takes to run a test, the less frequently the test can be run, which in turn...