使用 unittest 模拟 urllib.request.urlopen答案

【问题标题】：Mocking urllib.request.urlopen using unittest使用 unittest 模拟 urllib.request.urlopen
【发布时间】：2021-12-18 12:04:00
【问题描述】：

我正在尝试模拟这个 urlopen 函数。从其他类似问题中得到了几个解决方案，但似乎都没有。

def lambda_handler(event, context):
   try:
        request = urllib.request.Request(url = URL, data = data, method = method, headers = headers)
        with urllib.request.urlopen(request) as httpResponse:
            # print(httpResponse.read().decode('utf-8'))
            string = httpResponse.read().decode('utf-8')
            response = json.loads(string)
            print(response)
            return response

尝试的方法：

class mock_request():
   class Request():
       ....
   def urlopen(*args, **krwargs):
       return {}

@mock.patch(.....urllib.request, mock_request)

【问题讨论】：

标签： request mocking urllib python-unittest

【解决方案1】：

我认为最简单的方法是修补 __enter__ + __exit__ 方法。只是一个例子：

def lambda_handler(event, context):
    try:
        # some request... just an example
        request = Request('https://restcountries.com/v3.1/name/belarus')
        with urllib.request.urlopen(request) as resp:
            string = resp.read().decode('utf-8')
            return json.loads(string)
    except Exception:
       pass

测试：

from unittest import TestCase, mock
from unittest.mock import Mock


class TestExample(TestCase):
    def test_lambda_handler(self):
        print(lambda_handler(1, 2))  # real result from restcountries

        open_mock = Mock(
            # resp.read().decode('utf-8') will return static value '[]'
            __enter__=Mock(return_value=Mock(read=Mock(return_value=Mock(decode=Mock(return_value='[]'))))),
            __exit__=Mock(),
        )
        with mock.patch('urllib.request.urlopen', return_value=open_mock):
            print(lambda_handler(1, 2))  # []

        # resp.read().decode('utf-8') will return dynamic values
        open_mock = Mock(
            __enter__=Mock(
                return_value=Mock(
                    read=Mock(return_value=Mock(decode=Mock(side_effect=[
                        '[{"name": "N S"}]',
                        '[{"name": "D G"}]']
                    )))
                )
            ),
            __exit__=Mock(),
        )

        with mock.patch('urllib.request.urlopen', return_value=open_mock):
            print(lambda_handler(1, 2))  # [{"name": "N S"}]
            print(lambda_handler(1, 2))  # [{"name": "D G"}]

【讨论】：