Exception when configuring expectations on method returning enum with abstract methods on JDK17

[adessaigne]

Hello,

In the following environment:

• JMockit 1.49
• Code built and tested using OpenJDK 17.0.2

When testing the following code

public class ServiceTest {
    public enum Flag {
        ENABLED {
            @Override
            Flag flip() {
                return DISABLED;
            }
        },

        DISABLED {
            @Override
            Flag flip() {
                return ENABLED;
            }
        };

        abstract Flag flip();
    }

    public interface Service {
        Flag flag();
    }

    @Mocked
    Service m_service;

    @Test
    public void shouldWork() {
        new Expectations() {{
            m_service.flag();
            result = Flag.ENABLED;
        }};

        System.out.println(m_service.flag());
    }
}

We have the following exception

java.lang.IncompatibleClassChangeError: class demo.$Subclass_Flag_flag cannot inherit from sealed class demo.ServiceTest$Flag
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1012)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:874)
    at demo.ServiceTest$1.<init>(ServiceTest.java:38)
    at demo.ServiceTest.shouldWork(ServiceTest.java:37)

It fails because it tries to mock the enum. Is there a way to say "do not try to mock the result, I will provide it to you"? Thank you

[adessaigne]

Here is a dirty hack I've found that works around this issue

public static <T> void setJMockitDefaultValue(Class<T> aClass, T defaultValue) {
    requireNonNull(aClass, "The class must be defined");
    requireNonNull(defaultValue, "The default value must be defined");

    try {
        final Field field = DefaultValues.class.getDeclaredField("TYPE_DESC_TO_VALUE_MAP");
        field.setAccessible(true);
        final Map<String, Object> map = (Map<String, Object>) field.get(null);
        map.put(aClass.descriptorString(), defaultValue);
    } catch (Exception e) {
        throw new RuntimeException("Cannot initialize JMockit properly", e);
    }
}