Using Python 3.5, requests==2.18.4, Flask==0.12.2, urllib3==1.22
I have a method some_method
in my main server.py
file, that is supposed to make a POST
to some url with some data:
def some_method(url, data):
...
error = None
try:
response = requests.post(url, json=data)
except requests.exceptions.ConnectionError as e:
...
app.logger.error(...)
response = None
error = str(e)
return error, response
The server file defines: app = Flask(__name__)
, and some_method
is called from @app.route(... methods=['PATCH'])
.
If this method throws an error, the route will eventually return a 500
.
Tests are run from a test file importing the app with import server
and app = server.app
, using unittest
, and importing mock.patch
.
I am able to test the overall app behavior, with a test that shows that the app route behave as expected when the method returns an error and seeing that the route terminates at the right spot:
class ServerTestCase(unittest.TestCase):
...
@patch('server.some_method')
def test_route_response_status_500_when_throws(self, mock_response):
mock_response.return_value = 'some_error_string', None
response = self.app.patch(some_url, some_data, content_type='application/json')
self.assertEqual(response.status_code, 500)
However, I would really like to have another test to test some_method
in isolation:
requests.post
to throw requests.exceptions.ConnectionError
app.logger
and assert that it logged during the execution)Mock the requests.post
function, and on the mock set the side_effect
attribute to the desired exception:
@patch('requests.post')
def test_request_post_exception(self, post_mock):
post_mock.side_effect = requests.exceptions.ConnectionError()
# run your test, code calling `requests.post()` will trigger the exception.
From the linked documentation:
This can either be a function to be called when the mock is called, an iterable or an exception (class or instance) to be raised.
[...]
An example of a mock that raises an exception (to test exception handling of an API):
>>> mock = Mock() >>> mock.side_effect = Exception('Boom!') >>> mock() Traceback (most recent call last): ... Exception: Boom!
(Bold emphasis mine).
This is also covered in the Quick Guide section:
side_effect
allows you to perform side effects, including raising an exception when a mock is called:>>> mock = Mock(side_effect=KeyError('foo')) >>> mock() Traceback (most recent call last): ... KeyError: 'foo'
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