public void UpdateBook_NonExistingBook_ReturnsNotFound()
        {
            mockService.Setup(s => s.UpdateBook(It.IsAny <UpdateBookDto>()))
            .Returns(BookTestData.UpdateBookServiceResponseNullData());

            BookController bookController = new BookController(mockService.Object);

            UpdateBookDto updatedBook = BookTestData.UpdateBookDto();
            var           result      = bookController.UpdateBook(updatedBook);

            Assert.That(result, Is.InstanceOf <NotFoundObjectResult>());
        }