when does not throw MissingMethodInvocationException

[ac-rdn]

Given these two classes

class Greeting { String sayHi() { return "Hi!"; } }
class Person {
    String greet(Greeting greeting) { return sayHi(greeting); }
    String sayHi(Greeting greeting) { return greeting.sayHi(); /* LINE1 */ }
}

And the following test class

import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.when;

@ExtendWith(MockitoExtension.class)
class PersonTest {
    @Mock
    private Greeting greeting;

    @Test
    void greet() {
        Person person = new Person();
        when(person.sayHi(greeting)).thenReturn("Hello!"); // LINE2

        String actual = person.greet(greeting);

        assertThat(actual).isEqualTo("Hello!");
    }
}

I was astonished to see that this test runs successfully, because I would have expected a MissingMethodInvocationException being thrown on LINE2 as I am trying to stub a method call on a non-mock object. If you change LINE1 to return "Hello!"; the expected MissingMethodInvocationException is thrown. Why is this exception not thrown in the SSCCE? 😕

[yanapeycheva]

Hello,
can I contribute on this issue?