python how to mock a method?

Question

I want to test a http post method, this method will call some service, but the service cannot work in local test machine, so I want to mock it.

test.py:

@route(bp, '/count', methods=['POST'])
def count():
   from module import service
   ...
   total, ids = service(id, page, count) // total is a integer, ids is a list.
   ...
   return {'total': total, 'ids': ids}

test case:

@mock.patch("module.service")
def test_search_user(self, mock_service):
    mock_service.return_value=(1, [])

    url = url_for('users.count')
    params = { .... }

    response = self._test_app.post_json(
        url, params, headers=self.request_headers, expect_errors=True)

    self.assertEqual(response.status_code, 200)

but test case is always failed, it tried to call service method, but it cannot work on my machine. I just want to mock it, but doesn't work.

Anyone can help me! Thanks in advance!

According to @syntonym answer, my test case should be wrote like this:

@mock.patch("test.service")
def test_search_user(self, mock_service):
    mock_service.return_value=(1, [])

Answer 1

@mock.patch actually takes the lookup name - not the place where the object you want to patch acutally resides. The documentation reads :

patch() works by (temporarily) changing the object that a name points to with another one. [...] The basic principle is that you patch where an object is looked up, which is not necessarily the same place as where it is defined.