Test Django user profile one-to-one link - django

Question

I'm adding a Profile to my Django app as a way to store more User information. Following https://simpleisbetterthancomplex.com/tutorial/2016/07/22/how-to-extend-django-user-model.html#onetoone
However I'm getting an error when testing it. I'm using the default User model from django.contrib.auth.
models.py
from django.db import models
from django.contrib.auth import get_user_model
from django.db.models.signals import post_save
from django.dispatch import receiver
class Profile(models.Model):
user = models.OneToOneField(get_user_model(), on_delete=models.CASCADE)
#receiver(post_save, sender=get_user_model())
def create_user_profile(sender, instance, created, **kwargs):
if created:
Profile.objects.create(user=instance)
#receiver(post_save, sender=get_user_model())
def save_user_profile(sender, instance, **kwargs):
instance.profile.save()
tests/test_model.py
from django.test import TestCase
from app.models import Profile
class ProfileModelTests(TestCase):
#classmethod
def setUpTestData(cls):
Profile.objects.create()
def test_can_create_profile(self):
pass
error
/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/psycopg2/__init__.py:144: UserWarning: The psycopg2 wheel package will be renamed from release 2.8; in order to keep installing from binary please use "pip install psycopg2-binary" instead. For details see: <http://initd.org/psycopg/docs/install.html#binary-install-from-pypi>.
""")
..........E............
======================================================================
ERROR: setUpClass (project-api.polls.tests.test_models.ProfileModelTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
psycopg2.IntegrityError: null value in column "user_id" violates not-null constraint
DETAIL: Failing row contains (158, null).
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/test/testcases.py", line 1002, in setUpClass
cls.setUpTestData()
File "/Users/user/programming/gatsby/project-api/polls/tests/test_models.py", line 86, in setUpTestData
Profile.objects.create()
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/models/manager.py", line 82, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/models/query.py", line 417, in create
obj.save(force_insert=True, using=self.db)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/models/base.py", line 729, in save
force_update=force_update, update_fields=update_fields)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/models/base.py", line 759, in save_base
updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/models/base.py", line 842, in _save_table
result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/models/base.py", line 880, in _do_insert
using=using, raw=raw)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/models/manager.py", line 82, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/models/query.py", line 1125, in _insert
return query.get_compiler(using=using).execute_sql(return_id)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/models/sql/compiler.py", line 1283, in execute_sql
cursor.execute(sql, params)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/backends/utils.py", line 68, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/utils.py", line 89, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/Users/user/.local/share/virtualenvs/project-api-HgI9cQzm/lib/python3.6/site-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
django.db.utils.IntegrityError: null value in column "user_id" violates not-null constraint
DETAIL: Failing row contains (158, null).
----------------------------------------------------------------------
Ran 22 tests in 2.198s
FAILED (errors=1)
Using existing test database for alias 'default'...
System check identified no issues (0 silenced).
Preserving test database for alias 'default'...

Answer 1

#receiver(post_save, sender=get_user_model())
With this code, you are listening to the save method of the User model to create a related Profile entry just in time, if there isn't one yet. This way, you can just go along creating new Users without worrying at creating and linking Profiles manually everytime.
Note that the reverse isn't covered: if you want to create a Profile entry directly, you must pass an existing User object to it, or else you will get an IntegrityError.
Solution: preferrably, stick to one main way to create user + profile pairs; in your case, just create a User and let the signal call the creation of the profile automatically.
class ProfileModelTests(TestCase):
#classmethod
def setUpTestData(cls):
get_user_model().objects.create()
def test_profile(self):
profile = get_user_model().objects.last().profile

Answer 2

The idea is Profile.objects.create(user=instance) if the user doesn't exist yet an IntegrityError exception will be thrown since no user_id to be found. The signals will listen when the user will be created not the reverse.
In your testcase Profile.objects.create() will try to create a One-To-One relation with a user that doesn't exist.