Python how to mock a function within another function

Question

I have made some changes to a functionality which is breaking the unit tests. Previously i had a common.py containing the function request_url:

import requests

def request_url(method, url):
    return _request_url(method, url)

def _request_url(method, url):
    return requests.request(method, url)

And this was the test:

@mock.patch("requests.request", autospec=True)
def test_request_url_200(self, mock_request):

    response = mock.MagicMock()
    response.status_code = 200
    method = mock.sentinel.method
    path = "url"

    result = common.request_url(
        method,
        path
    )

    self.assertListEqual([
        mock.call(
            mock.sentinel.method,
            "url"
        ),
    ], list(mock_request.mock_calls))

    self.assertListEqual([mock.call.raise_for_status()], list(response.mock_calls))
    self.assertEqual(mock_request.return_value, result)

After the changes in functionality, instead of simply calling requests.request, i have first initiated a session, mounted a TLS Adapter and then called the session's request function like this:

def _request_url(method, url):
    session = requests.session()
    adapter = TlsAdapter(ssl.OP_NO_TLSv1 | ssl.OP_NO_TLSv1_1)
    session.mount("https://", adapter)
    return response = session.request(method, url)

Here, i am not sure how to exactly mock session.request since that is available through the session variable. I tried patching requests.session.request but that does not work here.

Does anyone have any idea how can this function be mocked?

thanks!

Answer 1

I think the reason in @mock.patch(...). You set autospec=True, but your mock_request doesn't return data(in your case everytime - Mock). The documentation says:

If you set autospec=True then the mock will be created with a spec from the object being replaced. All attributes of the mock will also have the spec of the corresponding attribute of the object being replaced. ...

Try to call:

print(mock_request.return_value) # <MagicMock name='request()()' id='4343989392'>
# or
# print(mock_request.return_value.return_value) # <MagicMock name='request()()()' id='4344191568'>

As you can see requests.request was 'mocked' but doesn't return any data. You can set expected data using return_value or side_effect. Here an example:

from unittest import TestCase
import mock
from common import request_url


class MyTestExample(TestCase):

    def test_request_url_1(self):
        mocked_request = mock.patch('requests.request', side_effect=['one', 'two', 'tree', ])
        mocked_request.start()
        # request_url(...) will return item from list
        self.assertEqual('one', request_url('test', 'url'))
        self.assertEqual('two', request_url('test', 'url'))
        self.assertEqual('tree', request_url('test', 'url'))

        mocked_request.stop()

    def test_request_url_2(self):
        result = {'my': 'dict'}
        mocked_request = mock.patch('requests.request', return_value=result)
        mocked_request.start()
        # request_url(...) will return static data 
        self.assertEqual(result, request_url('test', 'url'))
        self.assertEqual(result, request_url('test', 'url'))
        self.assertEqual(result, request_url('test', 'url'))

        mocked_request.stop()

So, you need just describe expected data. Also you can mock API using httpretty.

Hope this helps.