Detect annotations on overridden super type methods

[sormuras]

Overview

In JUnit 4, if @Test is declared on an abstract method in a superclass, then any concrete implementation of the method is not required to redeclare the @Test annotation. However, JUnit Jupiter currently does not support implicitly inherited annotations on overridden methods.

This is an unintentional difference between JUnit 4 and JUnit Jupiter.

Related Discussions

• https://stackoverflow.com/questions/45162254/why-do-junit-5-tests-not-inherit-test-annotation-from-abstract-classes
• @Ignore not taking effect when used on an overriden test method junit4#695
• bug in ignore an overriding method junit4#468
• stefanbirkner/junit@2607752

Deliverables

• Tweak internal annotation utilities to find implicitly inherited annotations on overridden methods.
• Tweak internal annotation utilities to find implicitly inherited repeated annotations on overridden methods.

[sbrannen]

FYI: I have updated the title and description.

[sbrannen]

Works in JUnit 4

import org.junit.Before;
import org.junit.Test;

public abstract class AbstractTests {

	@Before
	public abstract void before();

	@Test
	public abstract void test();

}

public class FooTests extends AbstractTests {

	@Override
	// @Before
	public void before() {
		System.err.println("before");
	}

	@Override
	// @Test
	public void test() {
		System.err.println("test");
	}

}

[sbrannen]

Does not work in JUnit Jupiter 5.0 M5

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

public abstract class AbstractTests {

	@BeforeEach
	public abstract void before();

	@Test
	public abstract void test();

}

public class FooTests extends AbstractTests {

	@Override
	// @BeforeEach
	public void before() {
		System.err.println("before");
	}

	@Override
	// @Test
	public void test() {
		System.err.println("test");
	}

}

[sormuras]

Does not work in JUnit Jupiter 5.0 M5

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

interface InterfaceTests {

	@BeforeEach
	void before();

	@Test
	void test();

}

public class BarTests implements InterfaceTests {

	@Override
	// @BeforeEach
	public void before() {
		System.err.println("before");
	}

	@Override
	// @Test
	public void test() {
		System.err.println("test");
	}

}

[sbrannen]

My preliminary analysis of this functionality in JUnit 4 leads me to believe that the behavior is perhaps accidental, especially in light of explicit documentation within JUnit 4's BlockJUnit4ClassRunner such as the following.

    /**
     * Returns the methods that run tests. Default implementation returns all
     * methods annotated with {@code @Test} on this class and superclasses that
     * are not overridden.
     */
    protected List<FrameworkMethod> computeTestMethods() {
        return getTestClass().getAnnotatedMethods(Test.class);
    }

A round of debugging led me to the fact that the following is actually what JUnit 4 tracks as the "test method" in such cases.

[public void org.junit.platform.AbstractTests.test()]

In summary: it appears that JUnit 4 in fact does not have any special reflective code in place to support "implicit inheritance" of annotations of methods. Rather, it only works coincidentally since JUnit 4 erroneously (?) tracks annotated abstract methods. If a concrete method (that overrides an annotated abstract method) is not annotated, it simply gets ignored since it is in fact "not a test method". Then the execution of the abstract method just happens to work by chance (?) since the methods have the same name.

In light of these findings, I am removing the "bug" label, adding the "team discussion" label, and moving this issue to 5.0 RC1.