如何使用python模拟库和decorator与unittest lib？

Question

I am trying to use mock python library, and decided to use a decorator to hide a few repetitive operations for setting mock side_effect vars with corresponding replacement methods.

So far I have the following code, which does not enter the tests, it basically does nothing. Any ideas on how to fix this? Thanks!

import unittest
from mock import patch

# Replacement method for requests.get call
def mock_requests_get(url=None, **kwargs):
    if url == URL1:
        return {'url':url, 'status_code':200, 'status':'success'}

    if url == URL2: A
        return {'url':url, 'status_code':403}

# Replacement method for requests.post call
def mock_requests_post(url, data=None, **kwargs):
    if url == URL1 and data['data']=='go':
        return {'url':url, 'status_code':200, 'status':'success'}

    if url == URL2 and data['data']!='gogo':
        return {'url':url, 'status_code':403}

# Decorator which sets mock replacement methods
def mock_type(method=''):
    def _mock(func):
        def _decorator(mock_get, mock_post, *args, **kwargs):
            print method
            if method == 'GET':
                mock_get.side_effect = mock_requests_get
            if method == 'POST':
                mock_post.side_effect = mock_requests_post
            func(mock_get, mock_post, *args, **kwargs)
        return _decorator
    return _mock

@patch('requests.post')
@patch('requests.get')
class TestKeywordsApi(unittest.TestCase):

    def setUp(self):
        self.ka = KeywordsApi()

    @mock_type('GET')
    def test_get(self, mock_get, mock_post):
        # Replace this code in mock_type decorator:
        #mock_get.side_effect=mock_requests_get

        print self.ka.get(URL1)
        print self.ka.get(URL2)

        # Do asserts

    @mock_type('POST')
    def test_post(self, mock_get, mock_post):
        # Replace this code in mock_type decorator:
        #mock_post.side_effect=mock_requests_post

        print self.ka.post(URL1, {'data':'go'})
        print self.ka.post(URL2, {'data':'go'})

        # Do asserts

Answer 1

Make sure to replace the functions in the execution namespace. Depending on the imports, your current code may or may not be replacing what you think it is replacing. The following does what I believe you were trying to do.

import kwmodule
import unittest, mock

def mock_requests_get(url=None, **kwargs):
    "Replacement method for requests.get call"
    pass

def mock_requests_post(url, data=None, **kwargs):
    "Replacement method for requests.post call"
    pass

@mock.patch('kwmodule.requests.post', mock_requests_post)
@mock.patch('kwmodule.requests.get', mock_requests_get)    
class TestKeywordsApi(unittest.TestCase):
     def setUp(self):
         self.ka = kwmodule.KeywordsApi()

However, you may be more successful with replacing get & post with autospecced MagicMock objects. If that doesn't work for you, then use your own custom replacement.

For instance, the following patch decorator would work if you know the order of calls to "get."

return_values = [{'url':url, 'status_code':200, 'status':'success'}, 
                 {'url':url, 'status_code':403}, 
                 AssertionError('Unexpected call.')]

@mock.patch('kwmodule.requests.get', autospec=True, side_effect=return_values)

This will return a "success" condition the first time it is called, an error the second time, and it will raise an AssertionError if it is called a third time. Nine times out of ten, I use side_effect instead of writing my own return generating function.