1. Security
Checking the app for any and all sorts of vulnerabilities that can leak sensitive data to malicious algorithms is priority number one, no exceptions. The app must be tested at every incremental stage of its development and on as many actual devices as possible and device simulators used only for unavailable devices.
Other factors like the integrity of the encryption can be assessed for parameters like, whether a previously documented encryption methodology is used down to the bit level. Latest patches and fixes for the methodology should be validated and updated.

2. Budget/Time to market
Testing can be a time-consuming process and it is very important to schedule in the expected time that will be taken up by testing in your strategy. Many organizations tend to underestimate how much time the testing process can take, get impatient, and then rush the process which invariably results in buggy apps. A similar argument can be made for the budget allocated for testing as well. An underfunded testing process will yield the same result as above.
It is an imperative that organizations allow ample time and allocate a budget to ensure the application is properly tested before hitting the market.

3. Shed App Size

The testing phase is a good time to shed the size of the app, which can potentially dissuade customers from even downloading the app. The size of the app, one of the few customer facing numbers, can be cut down via a number of techniques. A small app downloads and installs faster and doesn’t take much memory space.

4. Read Play Store/App Store Reviews
In the case of a newer version of the app is being tested, customer reviews from the App Store and Play Store must be thoroughly combed to identify common and the not so common issues that the customers are facing. Employing this strategy, can save time and keep the customers happy.

5. Legal considerations
Literally hundreds of details, accidental or otherwise can get an app banned from the App Store/Play Store. Testing is the last line of defense to check and double check or sometimes triple check details that can keep the app on the various mobile app marketplaces and get positive reviews.
In the case of global apps that will be used by people from a number of countries, factors like a government approved encryption methodology, data storage within a country’s shores, must be validated when testing.