Change MEDIA_URL to an absolute URL in tests

[itisnotyourenv]

Description

I recently noticed that in cases where we have a default value for models' ImageField like in the example below

class Book(models.Model):
    cover = models.ImageField(upload_to="images/", default=DEFAULT_IMAGE, verbose_name="Изображение")

and try to compare the field from the response with the expected field from a serializer

class TestUserViewSet:
    def test_get_user_by_id(self, api_client: APIClient, user: User, admin_user: User):
        url = reverse("api:users-detail", kwargs={"id": admin_user.id})
        expected_data = UserSerializer(admin_user).data

        response = api_client.get(url)

        assert response.status_code == status.HTTP_200_OK
        assert response.data.get("image") == expected_data.get("image")

we encounter a failure because Django adds a prefix "http://testserver" to the ImageField and for other areas that use MEDIA_URL.
{'image': 'http://testserver/media/default/user-logo.jpg'} != {'image': '/media/default/user-logo.jpg'}

Checklist:

• I've made sure that tests are updated accordingly (especially if adding or updating a template option)
• I've updated the documentation or confirm that my change doesn't require any updates

Rationale

This will help to avoid incomprehensible errors in tests and these changes can be quite in demand.

[browniebroke]

Thanks for your contribution.

Is there a reason to use a fixture to set this? Since it's a constant string, it's better to set it in the dedicated setting file for tests, as it's where other similar ones are set. The media_storage defined above is set via a fixture because it uses the pytest fixture tmpdir.

Small note that this URL prefix is actually added by DRF (https://github.com/encode/django-rest-framework/blob/7658ffd71d4ad07ddada20b2b9538b889ec02403/rest_framework/fields.py#L1539-L1554), to make the URL absolute. Although, it's true that it's calling an API from Django: https://github.com/django/django/blob/0016a4299569a8f09ff24053ff2b8224f7fa4113/django/http/request.py#L201.

Which leads me to the fact that I'm slightly against this change, for the following reasons:

• By setting the MEDIA_URL value to an absolute URI, you're hiding the fact that this transformation happens in the serialization, which is a kind of detail that I find useful to see in my tests.
• I'd argue that your test should compare the result of the serialization to something more static: assert response.data["image"] == "http://testserver/media/default/user-logo.jpg". The way it's written in your example feels to me like testing that 1 + 1 == 1 + 1, if that makes sense.

Although the counter argument to the 1st point here is that the MEDIA_URL is often absolute on prod anyway... I guess we could set it to an absolute URL different from the default server URL? e.g. https://testassets/media/.

[browniebroke]

Hey @itisnotyourenv 👋🏻 What do you think of my suggestions I mentioned above? Do you want to make any edits to this PR?

[itisnotyourenv]

Hey @itisnotyourenv 👋🏻 What do you think of my suggestions I mentioned above? Do you want to make any edits to this PR?

Sorry bro. I forgot about this PR, and didn't notice your last question. Thanks for merging