Inconsistent behaviour of @InjectMocks annotation

[el-hopaness-romtic]

Consider classes A and B

public class A {
    String call() {
        return null;
    }
}

public class B extends A {
}

And class C, contructor of which uses inctances of both A and B

public class C {
    private final A a;
    private final B b;

    C(A a, B b) {
        this.a = a;
        this.b = b;
    }

    public void callFields() {
        System.out.println("A " + a.call());
        System.out.println("B " + b.call());
    }
}

In that case following test does not behave consistently

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;

import static org.mockito.Mockito.when;

@ExtendWith(MockitoExtension.class)
class MockitoTest {
    @Mock
    A a;
    @Mock
    B b;
    @InjectMocks
    C c;

    @Test
    void test() {
        when(a.call()).thenReturn("A");
        when(b.call()).thenReturn("B");
        c.callFields();
    }
}

org.junit.jupiter:junit-jupiter:5.9.1
org.mockito:mockito-junit-jupiter:4.8.1
openjdk version "17.0.3" 2022-04-19 LTS

[HermitDede]

This issue caused me at least 1-2 hours to figure out. There was no clear explanation or warning for the root cause. It was behaving differently on each context. I came here to post this issue, but looks like this has been ongoing for 1 year 😞