Firebase Test Lab asks to upload two APKs:
How to build test APK?
Run: ./gradlew assembleDebugAndroidTest
./gradlew assembleDebugAndroidTest
The Test APK will be built in: app/build/outputs/apk/androidTest/<flavor>/debug/app-<flavor>-debug-androidTest.apk
app/build/outputs/apk/androidTest/<flavor>/debug/app-<flavor>-debug-androidTest.apk