Google Play error: cannot upload a test-only APK

Building your app through Android Studio 3.0 and later will add android:testOnly="true" to your application manifest, marking the APK as FLAG_TEST_ONLY for the PackageManager. More information on CommonsBlog here.

Attempting to install such an APK outside of Android Studio will fail with:

Failed to install app-debug.apk: Failure [INSTALL_FAILED_TEST_ONLY: installPackageLI]

Attempting to upload it to Google Play will also fail, with :

You cannot upload a test-only APK

There are four solutions to this:

Build from Android Studio

Simply select "Build APK(s)" from the "Build" menu in Android Studio.

Sign from Android Studio manually

Simply select "Generate Signed APK..." from the "Build" menu in Android Studio. Provide the keystore and enter the signing details in the dialog that displays.

Build through Gradle

You can of course simply execute Gradle from the terminal for some automation, for instance if your deployment cycle runs through CI (which I highly recommend!):

./gradlew assembleRelease

(Alternatively, you may prefer running this Gradle task from the Gradle pane from within Android Studio.)

Disable this feature in Android Studio

If you don't like this behavior, you may elect to add this flag to your gradle.properties. Beware that the test flag is for your own protection, so you don't accidentally publish a test-only APK!

# Disble testOnly mode for Android Studio
android.injected.testOnly=false

Looks like I found something very related: ADB Install Fails With INSTALL_FAILED_TEST_ONLY

I'm using 2.4.0-alpha6 of gradle plugin and that's seems to be far from ready to be used for production.

So the solution is to use the latest stable gradle plugin:

classpath 'com.android.tools.build:gradle:2.3.1'