It looks like you both want to mock what happens when userService.getUserById()
is called, and also verify that setPasswordChangeRequired(true)
is called on that returned object.
You can accomplish this with something like:
UserService userService = mock(UserService.class);
User user = mock(User.class);
when(userService.getUserById(anyLong())).thenReturn(user);
...
// invoke the method being tested
...
verify(user).setPasswordChangeRequired(true);