单元测试Django：模拟外部API，正确的方法是什么？

Question

我在理解模拟如何工作以及如何使用模拟对象编写单元测试时遇到问题。每当模型调用save（）方法时，我都想模拟一个外部api调用。我的代码： models.py

from . import utils

class Book(Titleable, Isactiveable, Timestampable, IsVoidable, models.Model):
   title
   orig_author
   orig_title
   isbn 

    def save(self, *args, **kwargs):
        if self.isbn:
            google_data = utils.get_original_title_and_name(self.isbn)
            if google_data:
                self.original_author = google_data['author']
                self.original_title = google_data['title']
        super().save(*args, **kwargs)

utils.py

def get_original_title_and_name(isbn, **kawargs):
    isbn_search_string = 'isbn:{}'.format(isbn)
    payload = {
        'key': GOOGLE_API_KEY,
        'q': isbn_search_string,
        'printType': 'books',
    }
    r = requests.get(GOOGLE_API_URL, params=payload)
    response = r.json()
    if 'items' in response.keys():
        title = response['items'][THE_FIRST_INDEX]['volumeInfo']['title']
        author = response['items'][THE_FIRST_INDEX]['volumeInfo']['authors'][THE_FIRST_INDEX]

        return {
            'title': title,
            'author': author
        }
    else:
        return None

我开始阅读文档并编写测试：

test.py：

from unittest import mock
from django.test import TestCase
from rest_framework import status
from .constants import THE_FIRST_INDEX, GOOGLE_API_URL, GOOGLE_API_KEY

class BookModelTestCase(TestCase):
    @mock.patch('requests.get')
    def test_get_original_title_and_name_from_google_api(self, mock_get):
        # Define new Mock object
        mock_response = mock.Mock()
        # Define response data from Google API
        expected_dict = {
            'kind': 'books#volumes',
            'totalItems': 1,
            'items': [
                {
                    'kind': 'books#volume',
                    'id': 'IHxXBAAAQBAJ',
                    'etag': 'B3N9X8vAMWg',
                    'selfLink': 'https://www.googleapis.com/books/v1/volumes/IHxXBAAAQBAJ',
                    'volumeInfo': {
                        'title': "Alice's Adventures in Wonderland",
                        'authors': [
                            'Lewis Carroll'
                        ]
                    }
                }
                    ]
            }

        # Define response data for my Mock object
        mock_response.json.return_value = expected_dict
        mock_response.status_code = 200

        # Define response for the fake API
        mock_get.return_value = mock_response

第一重要的是，我不能写target的@mock.patch是正确的。如果定义target为utuls.get_original_title_and_name.requests.get，我得到ModuleNotFoundError。我也无法理解如何对外部API进行虚假调用并验证接收到的数据（如果已经定义了，是否需要接收数据mock_response.json.return_value = expected_dict?），以及验证我的save（）方法是否正常工作？

如何为这种情况编写测试？有人可以向我解释这种情况吗？

Answer 1

您应该嘲笑被测代码的直接合作者。因为Book那是utils。因为utils那是requests。

所以对于BookModelTestCase：

class BookModelTestCase(TestCase):

    @mock.patch('app.models.utils')
    def test_save_book_calls_google_api(self, mock_utils):
        mock_utils.get_original_title_and_name.return_value = {
            'title': 'Google title',
            'author': 'Google author'
        }

        book = Book(
            title='Some title',
            isbn='12345'
        )
        book.save()

        self.assertEqual(book.title, 'Google title')
        self.assertEqual(book.author, 'Google author')
        mock_utils.get_original_title_and_name.assert_called_once_with('12345')

然后您可以创建一个单独的测试用例进行测试get_original_title_and_name：

class GetOriginalTitleAndNameTestCase(TestCase):

    @mock.patch('app.utils.requests.get')
    def test_get_original_title_and_name_from_google_api(self, mock_get):
        mock_response = mock.Mock()
        # Define response data from Google API
        expected_dict = {
            'kind': 'books#volumes',
            'totalItems': 1,
            'items': [
                {
                    'kind': 'books#volume',
                    'id': 'IHxXBAAAQBAJ',
                    'etag': 'B3N9X8vAMWg',
                    'selfLink': 'https://www.googleapis.com/books/v1/volumes/IHxXBAAAQBAJ',
                    'volumeInfo': {
                        'title': "Alice's Adventures in Wonderland",
                        'authors': [
                            'Lewis Carroll'
                        ]
                    }
                }
                    ]
            }

        # Define response data for my Mock object
        mock_response.json.return_value = expected_dict
        mock_response.status_code = 200

        # Define response for the fake API
        mock_get.return_value = mock_response

        # Call the function
        result = get_original_title_and_name(12345)

        self.assertEqual(result, {
            'title': "Alice's Adventures in Wonderland", 
            'author': 'Lewis Carroll'
        })
        mock_get.assert_called_once_with(GOOGLE_API_URL, params={
            'key': GOOGLE_API_KEY,
            'q': 'isbn:12345',
            'printType': 'books',
        })