AndroidJUnit4.class is deprecated: How to use androidx.test.ext.junit.runners.AndroidJUnit4?

According to the documentation for AndroidJUnit4,

1. The gradle file should contain the following line:

androidTestImplementation 'androidx.test.ext:junit:1.1.1'

2. Change test class to AndroidJUnit4ClassRunner from AndroidJUnit4

If it still doesn't work, make sure that you clean and/or rebuild your project. Also you can check the current version directly in Google's maven repository

If you've tried @MarcelGangwisch's solution and your build fails saying it can't find the resource AND you also cleaned/rebuilt your project and it still doesn't work, try this: (based also on @KrzysztofDziuba's solution)

In your gradle file where you changed the dependency, make sure you are adding it as the type you need, ie.:

For UI tests:

androidTestImplementation 'androidx.test.ext:junit:1.1.0'

For Unit tests:

testImplementation 'androidx.test.ext:junit:1.1.0'

In my instance I added it as both and now it works.

For me the following steps worked:
1. Replace the androidx libraries with the one posted here . my final app/build.gradle looked like this:

android {
    ...
    defaultConfig {
        ...
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

    }
    ...
}

dependencies {
    ...
    testImplementation 'junit:junit:4.12'

    // Core library
    androidTestImplementation 'androidx.test:core:1.2.0'

    // AndroidJUnitRunner and JUnit Rules
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test:rules:1.2.0'

    // Assertions
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.ext:truth:1.2.0'
    androidTestImplementation 'com.google.truth:truth:0.42'

    // Espresso dependencies
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

}

I then manually replaced the imported modules in my ExampleInstrumentTest.java class with latest classes:

import androidx.test.internal.runner.junit4.AndroidJUnit4ClassRunner;
import androidx.test.platform.app.InstrumentationRegistry;
import androidx.test.rule.ActivityTestRule;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;

@RunWith(AndroidJUnit4ClassRunner.class)
public class ExampleInstrumentedTest {
    ...
    @Rule
    public final ActivityTestRule<MainActivity> main = new ActivityTestRule<>(MainActivity.class, true);

    @Before
    public void init() {
        ...
    }
    @Test
    public void listCount() {
        ...
    }

    @Test
    public void useAppContext() {
        Context appContext = InstrumentationRegistry.getInstrumentation().getTargetContext();

        Assert.assertEquals("in.curioustools.aad_x_testing2", appContext.getPackageName());
        System.out.println("useAppContext : Test Ran");
    }
}

The thing that was bugging me was the fact that InstrumentationRegistery class was still deprecated. So i used InstrumentationRegistry.getInstrumentation().getTargetContext(); from androidx.test.platform.app.InstrumentationRegistry class.