No tests found when running instrumented tests with AndroidX

Question

I'm trying to run the standard ExampleInstrumentedTest in my Android project (which uses AndroidX), but get "No tests found" error instead. I've looked through the other questions and the documentation and I'm pretty sure I've done everything right, but maybe I'm overlooking anything?

Here is my app's build.gradle:

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-kapt'

android {
    compileSdkVersion 28
    defaultConfig {
        minSdkVersion 24
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.ext.junit.runners.AndroidJUnit4"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    // Gradle automatically adds 'android.test.runner' as a dependency.
    useLibrary 'android.test.runner'

    useLibrary 'android.test.base'
    useLibrary 'android.test.mock'
}

repositories {
    mavenCentral()
    maven {
        url("https://oss.sonatype.org/content/repositories/snapshots")
    }
    maven { url 'https://jitpack.io' }
}


dependencies {
    // Core library
    androidTestImplementation 'androidx.test:core:1.0.0'

    // AndroidJUnitRunner and JUnit Rules
    androidTestImplementation 'androidx.test:runner:1.1.0'
    androidTestImplementation 'androidx.test:rules:1.1.0'

    // Assertions
    androidTestImplementation 'androidx.test.ext:junit:1.0.0'
    androidTestImplementation 'androidx.test.ext:truth:1.0.0'
    androidTestImplementation 'com.google.truth:truth:0.42'

    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.0'
}

// More dependencies...    

and ExampleInstrumentedTest.java:

import org.junit.Test;
import org.junit.runner.RunWith;

import androidx.test.core.app.ApplicationProvider;
import androidx.test.ext.junit.runners.AndroidJUnit4;

import static org.junit.Assert.*;

@RunWith(AndroidJUnit4.class)
public class ExampleInstrumentedTest {
    @Test
    public void useAppContext() {
        Context appContext = ApplicationProvider.getApplicationContext();
        assertEquals("XXX", appContext.getPackageName());
    }
}

when I run the code, I get "No tests found".

Answer 1

I replaced -

testInstrumentationRunner "androidx.test.runner.AndroidJUnit4"

with -

testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"