Testing Django Rest Framework: how to test hyperlink relations? - django

Question

I'm trying to create a true unit test for a customized DjangoRestFramework Hyperlinked related field. But I cannot seem to get around this error:
django.core.exceptions.ImproperlyConfigured: Could not resolve URL for hyperlinked relationship using view name "relatedtestmodel-detail". You may have failed to include the related model in your API, or incorrectly configured the `lookup_field` attribute on this field.
And here is the unit test, stripped down to simplify the example:
from django.conf.urls import url
from django.test import TestCase, override_settings
from api_tests.models import APITestModel, RelatedTestModel
from api_tests.serializers import APITestModelSerializer
def dummy_view(request, pk):
pass
urlpatterns = [
url(r'/path/is/irrelevant/', dummy_view, name='relatedtestmodel-detail')
]
#override_settings(ROOT_URLCONF='tests.test_relations')
class HyperlinkedRelatedFieldTestCase(TestCase):
def setUp(self):
self.parent = APITestModel.objects.create()
self.child = RelatedTestModel.objects.create(parent=self.parent)
assert self.child.parent.id == self.parent.id
def test_to_internal_value_correct_error_message(self):
queryset = APITestModel.objects.all()
serializer = APITestModelSerializer(queryset, many=True, context={'request': None})
expected = [{'foo': 'bar'}]
self.assertEqual(serializer.data, expected)
I more or less lifted the test from https://github.com/encode/django-rest-framework/blob/master/tests/test_relations_hyperlink.py, because I figured who knows best how to unit test DRF than the makers of DRF? But as it stands, my test refuses to run. The error is raised during the test, when I attempt to access serializer.data for the assert.
Notice in particular that I override the settings with a custom urlpatterns (which is this same file, hence the urlpatterns at the top). So I don't understand why DRF thinks that url name doesn't exist - I can clearly see that my url conf in fact has ONLY that view name! I've even gone so far as to edit my actual URL conf and replace it with the single, named, dummy url pattern shown here, and removedthe settings override, just to be sure that it wasn't that the override_settings simply wasn't working, but even then I get the same error.
To my eye, the dummy url pattern is exactly the same as how DRF did it in their tests. Anyone have any ideas what is going on?
A bit more requested context:
api_tests.models:
from django.db import models
class APITestModel(models.Model):
pass
class RelatedTestModel(models.Model):
parent = models.ForeignKey(
APITestModel,
related_name='children',
related_query_name='child'
)
I do not have access to the traceback at this time, but I can confirm it did not pass through any of my code - it was all isolated to the DjangoRestFramework code, basically exclusively relations.py

Answer 1

Preamble
A few things this question is lacking
No definition of APITestModelSerializer
RelatedTestModel is not used in the test and therefore irrelevant for the example
No error stacktrace
No "useful" expected dict for the asserts
APITestModel has no fields so it can't be serialized (your test shouldn't even have run)
Minor things but still relevant
You are creating specific instances of APITestModel and RelatedTestModel in the setUp but in the test you serialize all instances of APITestModel
The line assert self.child.parent.id == self.parent.id should not be in the setUp. It should be in a separate test
My changes
I deleted all irrelevant information for this question mentioned above
I added an integer field to APITestModel
I changed the urlpatterns element from url(...) to path(...)
I added a regex to the relative path
The serializer is a subclass of HyperlinkedModelSerializer and includes fields "url" and "year"
My project and app urls.py files are the "stock" ones (not shown here) to emphasize that this test resolves the path in isolation.
Changed #override_settings(ROOT_URLCONF='tests.test_relations') to #override_settings(ROOT_URLCONF=__name__)
Code
models.py
from django.db import models
class APITestModel(models.Model):
year = models.IntegerField(null=False)
serializers.py
from rest_framework import serializers
from api.models import APITestModel
class APITestModelSerializer(serializers.HyperlinkedModelSerializer):
class Meta:
model = APITestModel
fields = ["url", "year"]
test_serializers.py
from django.test import TestCase, override_settings
from django.urls import path
from api.models import APITestModel
from api.serializers import APITestModelSerializer
urlpatterns = [
path('whateveryouwant/<int:pk>/', lambda request: None, name='apitestmodel-detail'),
]
#override_settings(ROOT_URLCONF=__name__)
class HyperlinkedRelatedFieldTestCase(TestCase):
def setUp(self):
# Populate db with APITestModel instances
_ = APITestModel.objects.create(year=1960)
_ = APITestModel.objects.create(year=1961)
_ = APITestModel.objects.create(year=1962)
def test_to_internal_value_correct_error_message(self):
queryset = APITestModel.objects.all()
serializer = APITestModelSerializer(queryset, many=True, context={'request': None})
expected = [
{'url': '/whateveryouwant/1/', 'year': 1960},
{'url': '/whateveryouwant/2/', 'year': 1961},
{'url': '/whateveryouwant/3/', 'year': 1962},
]
self.assertEqual(serializer.data, expected)
The other files in the project are the default ones created automatically by django + djangorestframework.
For future readers, I created a github project with this working code and can be found here: https://github.com/Alechan/drf_test_hyperlink_relations