1. 게시글 삭제 쿼리 작성

@Transactional
public void deleteById(int id) {
    Query query =
            em.createNativeQuery("delete from board_tb where id = ?");
    query.setParameter(1, id);

    query.executeUpdate();
}

2. 게시글 삭제 쿼리 테스트

@Test
public void deleteById_test(){
    // given
    int id = 1;

    // when
    boardNativeRepository.deleteById(id);

    // then
    List<Board> boardList = boardNativeRepository.findAll();
    assertThat(boardList.size()).isEqualTo(3);
}

3. 컨트롤러 delete 만들기

@PostMapping("/board/{id}/delete")
public String delete(@PathVariable Integer id){
    boardNativeRepository.deleteById(id);
    return "redirect:/";
}