如何对基于枚举的switch语句的默认情况进行单元测试

public class Animal {
    public enum Type {
        DOG, CAT, BIRD, FISH
    }

    public String getSound(Type type) {
        switch (type) {
            case DOG:
                return "Woof!";
            case CAT:
                return "Meow!";
            case BIRD:
                return "Chirp!";
            case FISH:
                return "Bubble!";
            default:
                return "Unknown animal sound";
        }
    }
}

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class AnimalTest {
    @Test
    public void testGetSound() {
        Animal animal = new Animal();

        assertEquals("Woof!", animal.getSound(Animal.Type.DOG));
        assertEquals("Meow!", animal.getSound(Animal.Type.CAT));
        assertEquals("Chirp!", animal.getSound(Animal.Type.BIRD));
        assertEquals("Bubble!", animal.getSound(Animal.Type.FISH));

        // 测试默认情况
        assertEquals("Unknown animal sound", animal.getSound(null));
    }
}