Error code

Android INSTALL_FAILED_TEST_ONLY

ANDROIDINSTALL_FAILED_TEST_ONLY
Android Error Code· An error code shown by Android or the Google Play Store.

What it means

The APK cannot be installed because it is marked as a test-only build.

How to fix it

  1. Install using adb with the -t flag (adb install -t app.apk).
  2. Rebuild the APK without the testOnly flag for production distribution.

Not affiliated with Android. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.