### Question:
BookServiceImpl implements BookService { @Override public boolean deleteById(Long id) { return bookMapper.deleteById(id) > 0; }  @Override boolean createBook(CreateOrUpdateBookDTO validator); @Override List<BookDO> getBookByKeyword(String q); @Override boolean updateBook(BookDO book, CreateOrUpdateBookDTO validator); @Override BookDO getById(Long id); @Override List<BookDO> findAll(); @Override boolean deleteById(Long id);  }### Answer:
@Test public void deleteById() { BookDO bookDO = new BookDO(); bookDO.setTitle(title); bookDO.setAuthor(author); bookDO.setImage(image); bookDO.setSummary(summary); bookMapper.insert(bookDO); bookService.deleteById(bookDO.getId()); BookDO hit = bookService.getById(bookDO.getId()); assertNull(hit); }