为什么我的单元测试失败，错误是“str”对象没有属性“cursor”？

Question

我有密码：

def get_address_query(trader_id, connection):
    cursor = connection.cursor()
    sql_address_data = "SELECT * FROM address where id = '%s' AND type = 'registered'"
    cursor.execute(sql_address_data, trader_id)
    address_query = cursor.fetchall()
    if address_query is None:
        raise Exception("address details do not exist")
    else:
        return address_query

我编写了以下测试：

    @mock.patch('lambda_function.pymysql')
    def test_get_address_query(self, mock_database_connection):
        mock_record = (('test',),('first',),('last',))
        mock_database_connection.cursor.return_value.fetchall.return_value = mock_record
        result = lambda_function.get_address_query('test', 'connection')
        self.assertEqual(result, mock_record)

但我犯了以下错误：

id = 'test', connection = 'connection'

    def get_address_query(id, connection):
>       cursor = connection.cursor()
E       AttributeError: 'str' object has no attribute 'cursor'

../lambda_function.py:92: AttributeError

我知道错误是由于我没有正确模拟connection.cursor.fetchall造成的，但我不确定如何正确操作。任何帮助都将不胜感激

Answer 1

您将字符串'connection'作为第二个参数传递给了get_address_query()

lambda_function.get_address_query('test', 'connection')

然后在get_address_query()内，它使用第二个参数connection（一个字符串）调用方法.cursor()

def get_address_query(trader_id, connection):
    cursor = connection.cursor()
    ...

这就像调用'connection'.cursor()显然会失败，因为str没有这样的方法

相反，您需要做的是将模拟对象mock_database_connection传递给connection参数。这样，所有对connection的调用（如connection.cursor()）都将使用配置的模拟对象

以下是您可能希望用作参考的最低测试代码：

import unittest
from unittest import mock


def get_address_query(trader_id, connection):
    cursor = connection.cursor()
    sql_address_data = "SELECT * FROM address where id = '%s' AND type = 'registered'"
    cursor.execute(sql_address_data, trader_id)
    address_query = cursor.fetchall()
    if address_query is None:
        raise Exception("address details do not exist")
    else:
        return address_query


class TestSample(unittest.TestCase):
    def test_get_address_query(self):
        mock_database_connection = mock.MagicMock()

        mock_record = (('test',),('first',),('last',))
        mock_database_connection.cursor.return_value.fetchall.return_value = mock_record

        result = get_address_query('test', mock_database_connection)

        self.assertEqual(result, (mock_record))


if __name__ == '__main__':
    unittest.main()

输出：

$ python3 test_src.py 
.
                                   
Ran 1 test in 0.002s

OK

• 现在，cursor.fetchall()的响应与我们在模拟对象mock_database_connection中配置的一样