IssueTracker

I spent hours yesterday trying to figure out why I  could not port a test from JUnit3 to JUnit4, it was failing with:

java.lang.RuntimeException: Delegate runner 'androidx.test.internal.runner.junit4.AndroidJUnit4ClassRunner' for AndroidJUnit4 could not be loaded.

Long story short, the problem was caused because JUnit3's setup was protected. You can easily reproduce it with the following test case:


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

import androidx.test.ext.junit.runners.AndroidJUnit4;

@RunWith(AndroidJUnit4.class)
public class YUNoClearTest {
   
    @Before
    public void preOk() {
        System.out.println("I'M PUBLIC, THEREFORE I EXIST!");
    }
   
    @Before
    protected void protectedByLaw() {
        System.out.println("DO YOU FEEL LUCKY, PUNK?");
    }
   
    @Test
    public void eureka() {
        System.out.println("FU!!");
    }
}


It will fail with:

STACKTRACE:
java.lang.RuntimeException: Delegate runner 'androidx.test.internal.runner.junit4.AndroidJUnit4ClassRunner' for AndroidJUnit4 could not be loaded.
        at androidx.test.ext.junit.runners.AndroidJUnit4.throwInitializationError(AndroidJUnit4.java:92)
        at androidx.test.ext.junit.runners.AndroidJUnit4.loadRunner(AndroidJUnit4.java:82)
        at androidx.test.ext.junit.runners.AndroidJUnit4.loadRunner(AndroidJUnit4.java:51)
        at androidx.test.ext.junit.runners.AndroidJUnit4.<init>(AndroidJUnit4.java:46)
        at java.lang.reflect.Constructor.newInstance0(Native Method)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:343)
        at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:104)
        at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:86)
        at androidx.test.internal.runner.junit4.AndroidAnnotatedBuilder.runnerForClass(AndroidAnnotatedBuilder.java:63)
        at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
        at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:26)
        at androidx.test.internal.runner.AndroidRunnerBuilder.runnerForClass(AndroidRunnerBuilder.java:153)
        at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
        at androidx.test.internal.runner.TestLoader.doCreateRunner(TestLoader.java:73)
        at androidx.test.internal.runner.TestLoader.getRunnersFor(TestLoader.java:104)
        at androidx.test.internal.runner.TestRequestBuilder.build(TestRequestBuilder.java:793)
        at androidx.test.runner.AndroidJUnitRunner.buildRequest(AndroidJUnitRunner.java:547)
        at androidx.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:390)
        at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:2189)
Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Constructor.newInstance0(Native Method)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:343)
        at androidx.test.ext.junit.runners.AndroidJUnit4.loadRunner(AndroidJUnit4.java:72)
        ... 17 more
Caused by: org.junit.runners.model.InitializationError
        at org.junit.runners.ParentRunner.validate(ParentRunner.java:418)
        at org.junit.runners.ParentRunner.<init>(ParentRunner.java:84)
        at org.junit.runners.BlockJUnit4ClassRunner.<init>(BlockJUnit4ClassRunner.java:65)
        at androidx.test.internal.runner.junit4.AndroidJUnit4ClassRunner.<init>(AndroidJUnit4ClassRunner.java:43)
        at androidx.test.internal.runner.junit4.AndroidJUnit4ClassRunner.<init>(AndroidJUnit4ClassRunner.java:48)
        ... 20 more


Then make protectedByLaw() public, and it will pass...