google3/third_party/java_src/junit/test/java/org/junit/tests/running/classes/parent/ParentRunnerClassLoaderTest.java

package org.junit.tests.running.classes.parent;

import static org.junit.Assert.assertEquals;

import java.lang.reflect.Field;
import java.net.URL;
import java.net.URLClassLoader;

import org.junit.Test;
import org.junit.runner.Description;
import org.junit.runner.notification.RunNotifier;
import org.junit.runners.BlockJUnit4ClassRunner;
import org.junit.runners.ParentRunner;
import org.junit.runners.model.FrameworkMethod;
import org.junit.runners.model.InitializationError;

public class ParentRunnerClassLoaderTest {
    @Test
    public void testClassRuleAccessToClassInAnotherClassLoader() throws Exception {
        Class<?> testClassWithOwnClassLoader = wrapToClassLoader(TestWithClassRule.class);

        runTestWithParentRunner(testClassWithOwnClassLoader);

        Field fieldWithReference = testClassWithOwnClassLoader.getDeclaredField("applyTestClass");
        Class<?> usedClass = (Class<?>) fieldWithReference.get(null);

        assertEquals("JUnitRunner can be located in own classLoader, so, " +
                        "Class.forName org.junit.runner.Description.getTestClass can not see " +
                        "in current classloader by execute Class.forName",
                testClassWithOwnClassLoader, usedClass
        );
    }

    @Test
    public void testDescriptionContainCorrectTestClass() throws Exception {
        Class<?> testClassWithOwnClassLoader = wrapToClassLoader(TestWithClassRule.class);
        ParentRunner<?> runner = new BlockJUnit4ClassRunner(testClassWithOwnClassLoader);

        Description description = runner.getDescription();
        assertEquals("ParentRunner accept already instantiate Class<?> with tests, if we lost it instance, and will " +
                "use Class.forName we can not find test class again, because tests can be " +
                "located in different ClassLoader",
                description.getTestClass(), testClassWithOwnClassLoader
        );
    }

    @Test
    public void testBackwardCompatibilityWithOverrideGetName() throws Exception {
        final Class<TestWithClassRule> originalTestClass = TestWithClassRule.class;
        final Class<?> waitClass = ParentRunnerClassLoaderTest.class;

        ParentRunner<FrameworkMethod> subParentRunner = new BlockJUnit4ClassRunner(originalTestClass) {
            @Override
            protected String getName() {
                return waitClass.getName();
            }
        };

        Description description = subParentRunner.getDescription();
        Class<?> result = description.getTestClass();

        assertEquals("Subclass of ParentRunner can override getName method and specify another test class for run, " +
                "we should  maintain backwards compatibility with JUnit 4.12",
                waitClass, result
        );
    }

    private void runTestWithParentRunner(Class<?> testClass) throws InitializationError {
        ParentRunner<?> runner = new BlockJUnit4ClassRunner(testClass);
        runner.run(new RunNotifier());
    }

    private Class<?> wrapToClassLoader(Class<?> sourceClass) throws ClassNotFoundException {
        URL classpath = sourceClass.getProtectionDomain().getCodeSource().getLocation();
        VisibleClassLoader loader = new VisibleClassLoader(new URL[]{classpath}, this.getClass().getClassLoader());
        Class<?> testClassWithOwnClassLoader = loader.findClass(sourceClass.getName());

        assert testClassWithOwnClassLoader != sourceClass;

        return testClassWithOwnClassLoader;
    }


    private static class VisibleClassLoader extends URLClassLoader {
        public VisibleClassLoader(URL[] urls, ClassLoader parent) {
            super(urls, parent);
        }

        @Override // just making public
        public Class<?> findClass(String name) throws ClassNotFoundException {
            return super.findClass(name);
        }
    }
}