Django: how to mock a class inside the API view - django

Question

Title might be a little confusing.
Say I have an APIView with a post method. Inside the post method, I introduced a class that has its own method. In this case, it's a class that deals with uploading to S3, which is something I want to skip when running unittest.
class SomeView(APIView):
def post(self):
# do something here
input1 = some_process(payload_arg1)
input2 = some_other_process(payload_arg2)
uploader = S3Uploader()
s3_response = uploader.upload_with_aux_fxn(input1, input2)
if s3_response['status_code'] == 200:
# do something else
return Response('Good job I did it!', status_code=200)
else:
return Response('noooo you're horrible!', status_code=400)
Real code has different function calls and responses, obviously.
Now I need to mock that uploader and uploader.upload_with_aux_fxn so I don't actually call S3. How do I mock it?
I tried in my test script
from some_place import S3Uploader
class SomeViewTestCase(TestCase):
def setUp(self):
self.client = APIClient()
uploader_mock = S3Uploader()
uploader_mock.upload_support_doc = MagicMock(return_value={'status_code': 200, 'message': 'asdasdad'}
response = self.client.post(url, payload, format='multipart')
But I still triggered S3 upload (as file shows up in S3). How do I correctly mock this?
EDIT1:
My attempt to patch
def setUp(self):
self.factory = APIRequestFactory()
self.view = ViewToTest.as_view()
self.url = reverse('some_url')
#patch('some_place.S3Uploader', FakeUploader)
def test_uplaod(self):
payload = {'some': 'data', 'other': 'stuff'}
request = self.factory.post(self.url, payload, format='json')
force_authenticate(request, user=self.user)
response = self.view(request)
where the FakeUplaoder is
class FakeUplaoder(object):
def __init__(self):
pass
def upload_something(self, data, arg1, arg2, arg3):
return {'status_code': 200, 'message': 'unit test', 's3_path':
'unit/test/path.pdf'}
def downlaod_something(self, s3_path):
return {'status_code': 200, 'message': '', 'body': 'some base64
stuff'}
unfortunately this is not successful. I still hit the actual class
EDIT 2:
I'm using Django 1.11 and Python 2.7, in case people need this info

Answer 1

I guess the correct approach to it would be save the file within a model with FileField, and then connect Boto to handle upload in production scenario.
Take a good look at:
https://docs.djangoproject.com/en/2.2/ref/models/fields/#filefield
and
https://django-storages.readthedocs.io/en/latest/backends/amazon-S3.html#model
this approach would preserve Django default behavior, making things more testable with Django's default test client.

Answer 2

Take a look at vcrpy. It records request to external API once and then replays answer every time you run your tests. No need to manually mock anything.

Answer 3

Here's an example of how I would mock that S3Uploader in an APITestCase.
from rest_framework import status
from unittest import mock
from unittest.mock import MagicMock
class SomeViewTestCase(APITestCase):
#mock.patch("path.to.view_file.S3Uploader")
def test_upload(self, s3_uploader_mock):
"""Test with mocked S3Uploader"""
concrete_uploader_mock = MagicMock(**{
"upload_with_aux_fxn__return_value": {"status_code": 200}
})
s3_uploader_mock.return_value = concrete_uploader_mock
response = self.client.post(url, payload, format='multipart')
self.assertEqual(response.status_code, status.HTTP_200_OK)
s3_uploader_mock.assert_called_once()
concrete_uploader_mock.upload_with_aux_fx.assert_called_once()

Answer 4

Try using MagicMock like below
from unittest import mock
from storages.backends.s3boto3 import S3Boto3Storage
class SomeTestCase(TestCase):
def setUp(self):
self.factory = APIRequestFactory()
self.view = ViewToTest.as_view()
self.url = reverse('some_url')
#mock.patch.object(S3Boto3Storage, '_save', MagicMock(return_value='/tmp/somefile.png'))
def test_uplaod(self):
payload = {'some': 'data', 'other': 'stuff'}
request = self.factory.post(self.url, payload, format='json')
force_authenticate(request, user=self.user)
response = self.view(request)