public int delete(String id) {
        return db.removeById(new ObjectId(id)).getN();
    }
@Test
    public void delete() {
        final TestDTO savedDto = dbService.save(newDto("hello"));

        assertThat(dbService.delete(savedDto.id)).isEqualTo(1);
        assertThat(dbService.delete(savedDto.id)).isEqualTo(0);

        assertThat(dbService.get(savedDto.id)).isNotPresent();
    }