Failed to instantiate test runner class androidx.test.internal.runner.junit4.androidjunit4classrunner

Answer:

When you encounter the error message “failed to instantiate test runner class
androidx.test.internal.runner.junit4.AndroidJUnit4ClassRunner”, it means that there is an issue with the test runner class used in your Android JUnit 4 tests.

The error message typically occurs when there is a mismatch between the version of AndroidJUnit4ClassRunner used in your code and the Android Support Library version. To resolve this issue, you need to ensure that both versions are compatible.

Here’s an example of how you can fix this error:

1. Open your build.gradle file.
2. Check the version of the AndroidJUnit4ClassRunner dependency specified in the dependencies block. It should be compatible with the version of the Android Support Library used in your project.

dependencies {
   // Check the version of the Android Support Library used in your project.
   implementation 'androidx.test:core:1.3.0'

   // Ensure that the version of AndroidJUnit4ClassRunner matches the Android Support Library version.
   testImplementation 'androidx.test.runner.AndroidJUnitRunner:1.3.0'
}

3. If the versions mismatch, update the AndroidJUnit4ClassRunner version to match the Android Support Library version.

dependencies {
   implementation 'androidx.test:core:1.3.0'
   testImplementation 'androidx.test.runner.AndroidJUnitRunner:1.3.0'
}

4. Sync your project to apply the changes and rebuild your project.
5. Run your tests again. The error “failed to instantiate test runner class
   androidx.test.internal.runner.junit4.AndroidJUnit4ClassRunner” should be resolved.