Mobile testing budgets get spent badly when teams chase device coverage for its own sake. What matters is the handful of journeys that carry your revenue — sign-up, log-in, the core task, payment — tested properly on the devices your users genuinely carry, which analytics will tell you rather than a generic popularity list. Beyond that, the failures we find most often are not on the happy path: what the app does on a weak connection or none at all, what happens when a call interrupts a payment, whether it survives the phone rotating or the OS reclaiming memory in the background, and whether it still works after an OS upgrade. Those are the bugs that generate one-star reviews, and they are the ones worth your testing time.