Installation failed with message INSTALL_FAILED_TEST_ONLY问题

　　An error INSTALL_FAILED_TEST_ONLY occurred when installing the project debug package to the mobile phone today, the mobile phone model vivoX21 version 8.1.0

Android studio reports error

solution:

1. Make sure the test phone has developer mode turned on and USB debugging turned on

2. Turn off the testOnly function in the gradle.properties file of the project in Android studio or add code

android.injected.testOnly=false

This perfectly solves the current problem