使用 python 模拟 urllib3.PoolManager().request 函数

Question

我有一个函数可以使用 urllib3.PoolManager() 发出 POST 请求。现在在单元测试中我想模拟所述请求但有一些困难。正确的做法是什么？

我的代码：

http = urllib3.PoolManager()
# my func
def func(event, context):
    ...
    resp = http.request('POST', url, body=encoded_msg)
    ...

# unit test
@patch('urllib3.PoolManager.request')
def test_lambda_handler(self, mock_instance):
    mock_instance.return_value = Mock(status = "200", data = "success")
    res = func(event, [])
    mock_instance.request.assert_called_once()

我收到此错误“AssertionError：预期 'request' 已被调用一次。已调用 0 次。”

Answer 1

由于您在 全局（或模块）作用域 中调用了 urllib3.PoolManager class 的构造函数。参考：#where-to-patch

module b does import a and some_function uses a.SomeClass. ... In this case the class we want to patch is being looked up in the module and so we have to patch a.SomeClass instead: @patch('a.SomeClass')

选项 1：在模拟 urllib3.PoolManager 之后导入 func class

lambda_handler.py:

import urllib3
import json

http = urllib3.PoolManager()
print('http: ', http)

def func(event, context):
    url = 'http://localhost:3000'
    data = {'attribute': 'value'}
    encoded_msg = json.dumps(data).encode('utf-8')
    resp = http.request('POST', url, body=encoded_msg)

test_lambda_handler.py:

import unittest
import json
from unittest import mock


class TestLambdaHandler(unittest.TestCase):

    @mock.patch('urllib3.PoolManager')
    def test_lambda_handler(self, mock_PoolManager):
        from lambda_handler import func
        mock_http = mock_PoolManager.return_value
        event = {}
        func(event, [])
        mock_http.request.assert_called_once_with('POST', 'http://localhost:3000', body=json.dumps({'attribute': 'value'}).encode('utf-8'))


unittest.main(verbosity=2)

测试结果：

test_lambda_handler (__main__.TestLambdaHandler) ... http:  <MagicMock name='PoolManager()' id='4475122928'>
ok

----------------------------------------------------------------------
Ran 1 test in 0.063s

OK
Name                                                Stmts   Miss  Cover   Missing
---------------------------------------------------------------------------------
src/Whosebug/69890084/lambda_handler.py            9      0   100%
src/Whosebug/69890084/test_lambda_handler.py      12      0   100%
---------------------------------------------------------------------------------
TOTAL                                                  21      0   100%

方案二：mock全局变量http，mock后不需要导入func

如果您在测试文件的顶部导入 lambda_handler 模块，模块 lambda_handler 将引用真实的 urllib3.PoolManager，这样就来不及模拟了。

import unittest
import json
from unittest import mock
from lambda_handler import func


class TestLambdaHandler(unittest.TestCase):
    @mock.patch('lambda_handler.http')
    def test_lambda_handler(self, mock_http):
        event = {}
        func(event, [])
        mock_http.request.assert_called_once_with('POST', 'http://localhost:3000', body=json.dumps({'attribute': 'value'}).encode('utf-8'))


unittest.main(verbosity=2)

测试结果：

http:  <urllib3.poolmanager.PoolManager object at 0x1104b2610>
test_lambda_handler (__main__.TestLambdaHandler) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.002s

OK
Name                                                Stmts   Miss  Cover   Missing
---------------------------------------------------------------------------------
src/Whosebug/69890084/lambda_handler.py            9      0   100%
src/Whosebug/69890084/test_lambda_handler.py      11      0   100%
---------------------------------------------------------------------------------
TOTAL                                                  20      0   100%

使用 python 模拟 urllib3.PoolManager().request 函数

Mocking urllib3.PoolManager().request function with python

python

unit-testing

mocking

urllib3