@Override
    public Set<City> findAllByCanton(Canton canton) {
        return cityRepository.findAllByCanton(canton).stream()
                .map(city -> City.builder()
                        .of(city)
                        .setCanton(canton)
                        .build())
                .collect(Collectors.toSet());
    }
@Test
    void findAllByCanton() {
        City city = createCity();
        Canton canton = city.getCanton();
        Mockito.when(cityRepository.findAllByCanton(canton))
                .thenReturn(Collections.singleton(city));
        Set<City> expected = Set.of(city);
        Set<City> actual = cityService.findAllByCanton(canton);
        ReflectionAssert.assertReflectionEquals(expected, actual);
    }