Your question is Testing Across Devices and OS. Take a moment with it on the right.
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Describe your strategy for testing across various device fragments and operating system versions. Explain how you would combine unit tests, Android instrumentation tests, emulator coverage, physical devices, and cloud device testing. Include how you would select a representative device and API-level matrix, handle OS-specific behavior, and run the strategy in CI while controlling test cost. Scope your answer to native Android applications using Kotlin, AndroidX, Gradle, and Firebase Test Lab.