AttributeError: This QueryDict instance is immutable for test cases

Question

I am trying to change my request.data dict to remove some additional field. It is working completely fine in views. But when I run test cases for the same, I get this error:

AttributeError: This QueryDict instance is immutable

Here is my viewset:

    def create(self, request, *args, **kwargs):

        context = {'view': self, 'request': request}

        addresses = request.data.pop("addresses", None)
        serializer = self.get_serializer(data=request.data, context=context)
        serializer.is_valid(raise_exception=True)
        response = super(WarehouseViewSet, self).create(request, *args, **kwargs)
        if addresses is None:
            pass
        else:
            serializer = self.get_serializer(data=request.data, context=context)
            serializer.is_valid(raise_exception=True)
            addresses = serializer.update_warehouse_address(request, addresses, response.data["id"])
            response.data["addresses"] = addresses
        return Response(data=response.data, status=status.HTTP_201_CREATED)

and here is my test case for the same view:

    def test_create_warehouse_authenticated(self):
        response = client.post(
            reverse('warehouse_list_create'),
            data={
                'name': self.test_warehouse['test_warehouse']['name'],
                'branch': self.test_warehouse['test_warehouse']['branch'],
            },
            **{'HTTP_AUTHORIZATION': 'Bearer {}'.format(
                self.test_users['test_user']['access_token']
            )},
        )

        self.assertEqual(response.status_code, status.HTTP_201_CREATED)

How to fix this error?

Pichardo

Answer 1

Try setting format='json' when calling client.post, rather than relying on the default. You don't mention which test client you are using, but you should be using the APIClient

client = APIClient()
client.login(...)
client.post(..., format='json')

Newer Django has a immutable QueryDict, so this error will always happen if you are getting your data from querystring or a multipart form body. The test client uses multipart by default, which results in this issue.

Last Resort: If you need to post multipart, and also modify the query dict (very rare, think posting image + form fields) you can manually set the _mutable flag on the QueryDict to allow changing it. This is

setattr(request.data, '_mutable', True)

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