Like it or not, developing mobile apps is no longer the wild west - domain of startups, dorm dwellers and cowboy coders. It's a professional business with enterprise grade infrastructure and continuous integration and delivery systems. One part of this that has really taken off is automated functional testing, also known as UI testing, and often discussed as part of the practice of Behavior Driven Development. Android and iOS now both have their own bundled frameworks for performing this testing, as well as other alternatives such as Calabash.
One question that has plagued owners and managers is, "Is automated functional testing really worth the investment?"