google3/third_party/java_src/junit/main/java/org/junit/runners/JUnit4.java

package org.junit.runners;

import org.junit.runners.model.InitializationError;
import org.junit.runners.model.TestClass;

/**
 * Aliases the current default JUnit 4 class runner, for future-proofing. If
 * future versions of JUnit change the default Runner class, they will also
 * change the definition of this class. Developers wanting to explicitly tag a
 * class as a JUnit 4 class should use {@code @RunWith(JUnit4.class)}, not,
 * for example in JUnit 4.5, {@code @RunWith(BlockJUnit4ClassRunner.class)}.
 * This is the only way this class should be used--any extension that
 * depends on the implementation details of this class is likely to break
 * in future versions.
 *
 * @since 4.5
 */
public final class JUnit4 extends BlockJUnit4ClassRunner {
    /**
     * Constructs a new instance of the default runner
     */
    public JUnit4(Class<?> klass) throws InitializationError {
        super(new TestClass(klass));
    }
}