你如何模拟PyMySQL的返回值以便在Python中进行测试？

Question

我正在尝试为将从MySQL数据库中提取数据的脚本设置一些测试.我在这里找到了一个看起来像我想做的例子,但它只给了我一个对象而不是结果:

<MagicMock name='pymysql.connect().cursor[38 chars]152'>

这是我正在使用的函数(simple.py):

import pymysql

def get_user_data():
    connection = pymysql.connect(host='localhost', user='user', password='password',
                                 db='db', charset='utf8mb4',
                                 cursorclass=pymysql.cursors.DictCursor)

    try:
        with connection.cursor() as cursor:
            sql = "SELECT `id`, `password` FROM `users`"
            cursor.execute(sql)
            results = cursor.fetchall()
    finally:
        connection.close()

    return results

而且测试:

from unittest import TestCase, mock
import simple

class TestSimple(TestCase):

    @mock.patch('simple.pymysql', autospec=True)
    def test_get-data(self, mock_pymysql):
        mock_cursor = mock.MagicMock()
        test_data = [{'password': 'secret', 'id': 1}]
        mock_cursor.fetchall.return_value = test_data
        mock_pymysql.connect.return_value.__enter__.return_value = mock_cursor

        self.assertEqual(test_data, simple.get_user_data())

结果:

AssertionError: [{'id': 1, 'password': 'secret'}] != <MagicMock name='pymysql.connect().cursor[38 chars]840'>

我正在使用Python 3.51

Answer 1

看起来你的mock缺少对游标的引用

mock_pymysql.connect.return_value.cursor.return_value.__enter__.return_value = mock_cursor

我总是发现模拟调用语法很尴尬,但MagicMock以迂回的方式显示出错了.它说它没有注册的返回值pymysql.connect.return_value.cursor

<MagicMock name='pymysql.connect().cursor[38 chars]840'>