django-rest-framework/tests/test_nullable_fields.py

from django.core.urlresolvers import reverse

from django.conf.urls import patterns, url
from rest_framework.test import APITestCase
from tests.models import NullableForeignKeySource
from tests.serializers import NullableFKSourceSerializer
from tests.views import NullableFKSourceDetail


urlpatterns = patterns(
    '',
    url(r'^objects/(?P<pk>\d+)/$', NullableFKSourceDetail.as_view(), name='object-detail'),
)


class NullableForeignKeyTests(APITestCase):
    """
    DRF should be able to handle nullable foreign keys when a test
    Client POST/PUT request is made with its own serialized object.
    """
    urls = 'tests.test_nullable_fields'

    def test_updating_object_with_null_fk(self):
        obj = NullableForeignKeySource(name='example', target=None)
        obj.save()
        serialized_data = NullableFKSourceSerializer(obj).data

        response = self.client.put(reverse('object-detail', args=[obj.pk]), serialized_data)

        self.assertEqual(response.data, serialized_data)