Test on multiple devices: Apps must be tested on actual devices, and on as many devices as possible, including Retina and non-Retina versions of iPad, iPhone, and iPod touch. Do not test only on the Simulator.
Apps configured as “ Universal ” (in Deployment Info > Devices) must include complete iPad xibs or Storyboards with the proper and expected user interface.
Apps that are iPhone only must still work on iPad devices in “ compatibility mode ” (also known as “ 2X mode ”).
Issues reported on 64-bit devices (for example, iPhone 5s) need to be tested on 64-bit devices.
Symbolicate crash logs: Any crash logs you have will need to be symbolicated. Symbolicated crash logs replace memory addresses with human-readable function names and line numbers and can often point directly to the line of code that caused a crash. To learn how to symbolicate crash logs, see Technical Note TN2151 “ Understanding and Analyzing iOS Application Crash Reports ”.
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Check differences in network connectivity: Use the “ Network Link Conditioner ” on your devices to test how your app behaves on a slow or unreliable internet connection. The behavior of the network that App Review or your customers use may be significantly different from the network you used during development. The Network Link Conditioner can be activated by navigating to Settings > Developer > Network Link Conditioner on your development device.
Test every language setting your app supports: Differences in localizations can cause different resources to be loaded, and for numbers and dates to be parsed or displayed differently. Remember to test each language setting on each device also.
Test data “ edge cases ”: Make sure you ’ ve tested app behavior when there are no Contacts, no photos in the Camera Roll, no Facebook friends, no Twitter followers and so on. Conversely, also check for a large number of contacts, photos and so on.