public void giveWine(Royalty r) {
    r.getDrink();
  }
@Test
  void testGiveWine() {
    final var royalty = mock(Royalty.class);
    final var servant = new Servant("test");
    servant.giveWine(royalty);
    verify(royalty).getDrink();
    verifyNoMoreInteractions(royalty);
  }