During Q1 of this year (1 January to 31 March), we gathered a significant amount of data from Testdroid Cloud on tests done by many mobile app and game developers. Testdroid Cloud is an online cloud-based platform for mobile developers to test that their apps work perfectly on the devices that their customers use.
During this period, over 17.7 million tests were run on 288 distinct Android hardware models. To be clear, different versions of some popular models were tested but are counted in the data as one distinct device (such as the Samsung Galaxy S4 GT-i9505 running 4.2.2, API level 17). Some popular devices also had different versions of a single OS, such as the Google Nexus 7 ME370T with Android OS version 4.1.2 (API level 16), 4.2.2 (API level 17) and 4.3 (API level 18).
All tests were automated, using standard Android instrumentation and different test-automation frameworks. In case you are not familiar with instrumentation, Android has a tutorial that explains basic test automation. Also, the tests caught problems through logs, screenshots, performance analysis, and the success-failure rate of test runs.
Note: The data includes all test results, from the earliest stage (=APK ready) to when the application gets “finalized.” Therefore, it includes the exact problems that developers encountered during this process.