How to use @InjectMocks to inject dependency with same type?

Question

I have a User class which has a constructor with two parameter of same type.

public class User {
    Dependency dependency1;
    Dependency dependency2;
    User(Dependency dependency1,Dependency dependency2){
        this.dependency1=dependency1;
        this.dependency2=dependency2;
    }
    public void test(){
        dependency1.print();
        dependency2.print();
    }
}

In my test, I have two Spy Dependency and I want them to be injected like new User(dependency1,dependency2) .

@ExtendWith(MockitoExtension.class)
public class InjectMocksTest {
    @InjectMocks
    User user;
    @Spy
    Dependency dependency1=new Dependency("dependent1");
    @Spy
    Dependency dependency2=new Dependency("dependent2");
    @Test
    void test(){
        user.test();
    }
}

But I find that dependency1 and dependency2 of User both refers to dependency1 in the test, like they are injected with new User(dependency1,dependency1) .

So how to achieve what I want with @InjectMocks annotation?

Answer 1

It appears that you can trick Mockito into injecting the mocks using Field injection if you create the object itself first, and set the arguments to null. This works for me:

@ExtendWith(MockitoExtension.class)
public class UserTest {
  @InjectMocks
  User user = new User(null, null);

  @Spy
  Dependency dependency1 = new Dependency("dependent1");
  @Spy
  Dependency dependency2 = new Dependency("dependent2");

  @Test
  void test() {
    user.test();
  }
}

Output:

dependent1
dependent2

However, this behavior is not documented, so I am not sure I would depend upon it.