Python 3 urlopen上下文管理器嘲諷

Question

我是新手測試，需要一些幫助。

假定具有這種方法：

from urllib.request import urlopen 

def get_posts(): 
    with urlopen('some url here') as data: 
     return json.loads(data.read().decode('utf-8')) 

是如何測試此方法的問題（使用mock.patch裝飾如果可能的話）？

我現在擁有的一切：

@mock.patch('mymodule.urlopen') 
def test_get_post(self, mocked_urlopen): 
    mocked_urlopen.__enter__ = Mock(return_value=self.test_data) 
    mocked_urlopen.__exit__ = Mock(return_value=False) 
    ... 

但它似乎並不奏效。

P.S.有什麼方便的方式來處理數據變量（哪種類型是HTTPResponse）在測試中，所以它可能只是簡單的字符串？

Answer 1

好吧，所以我寫了簡單的類來模擬上下文管理器。

class PatchContextManager: 

    def __init__(self, method, enter_return, exit_return=False): 
     self._patched = patch(method) 
     self._enter_return = enter_return 
     self._exit_return = exit_return 

    def __enter__(self): 
     res = self._patched.__enter__() 
     res.context = MagicMock() 
     res.context.__enter__.return_value = self._enter_return 
     res.context.__exit__.return_value = self._exit_return 
     res.return_value = res.context 
     return res 

    def __exit__(self, type, value, tb): 
     return self._patched.__exit__() 

用法：

with PatchContextManager('mymodule.method', 'return_string') as mocked: 
    a = mymodule.method(47) # a == 'return_string' 
    mocked.assert_called_with(47) 
    ... 

Answer 2

我用這個戰鬥爲好，終於想通了。 （Python 3語法）：

import urllib.request 
import unittest 
from unittest.mock import patch, MagicMock 

class TestUrlopen(unittest.TestCase): 
    @patch('urllib.request.urlopen') 
    def test_cm(self, mock_urlopen): 
     cm = MagicMock() 
     cm.getcode.return_value = 200 
     cm.read.return_value = 'contents' 
     cm.__enter__.return_value = cm 
     mock_urlopen.return_value = cm 

     with urllib.request.urlopen('http://foo') as response: 
      self.assertEqual(response.getcode(), 200) 
      self.assertEqual(response.read(), 'contents') 

    @patch('urllib.request.urlopen') 
    def test_no_cm(self, mock_urlopen): 
     cm = MagicMock() 
     cm.getcode.return_value = 200 
     cm.read.return_value = 'contents' 
     mock_urlopen.return_value = cm 

     response = urllib.request.urlopen('http://foo') 
     self.assertEqual(response.getcode(), 200) 
     self.assertEqual(response.read(), 'contents') 
     response.close()