Migrate all tests to JUnit5

public class JUnit3Builder extends RunnerBuilder {
    @Override
    public Runner runnerForClass(Class<?> testClass) throws Throwable {
        if (isPre4Test(testClass)) {
            return new JUnit38ClassRunner(testClass);
        }
        return null;
    }    boolean isPre4Test(Class<?> testClass) {
        return junit.framework.TestCase.class.isAssignableFrom(testClass);
    }
}