id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
25290	Warn against modifying objects created in setUpTestData	Markus Holtermann	Anjaliunni96	"Given the following models:

{{{#!python
from django.db import models


class RelObj(models.Model):
    def __repr__(self):
        return '<RelObj %d at id %x>' % (self.pk, id(self))


class Obj(models.Model):
    relobj = models.OneToOneField(RelObj)
    name = models.CharField(max_length=10, unique=True)
    val = models.IntegerField()

    def __repr__(self):
        return '<Obj %d at id %x>' % (self.pk, id(self))
}}}

And these tests:

{{{#!python
from django.db.utils import IntegrityError
from django.test import TestCase

from .models import Obj, RelObj


class ModelTests(TestCase):

    @classmethod
    def setUpTestData(cls):
        cls.relobj = RelObj.objects.create()
        cls.obj = Obj.objects.create(relobj=cls.relobj, name='foo', val=1)

    def test_1(self):
        self.assertEqual(self.obj.relobj, self.relobj)
        self.assertEqual(self.relobj.obj, self.obj)
        self.assertEqual(self.obj.name, 'foo')
        self.assertEqual(self.obj.val, 1)

    def test_2(self):
        with self.assertRaisesRegex(IntegrityError, 'app_obj_name_key'):
            Obj.objects.create(relobj=self.relobj, name='foo', val=2)

    def test_3(self):
        self.assertEqual(self.obj.relobj, self.relobj)
        self.assertEqual(self.relobj.obj, self.obj)
        self.assertEqual(self.obj.name, 'foo')
        self.assertEqual(self.obj.val, 1)
}}}

I get the following traceback on PostgreSQL

{{{#!python
Creating test database for alias 'default'...
..F
======================================================================
FAIL: test_3 (app.tests.ModelTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""/home/markus/Coding/django-test-app/app/tests.py"", line 26, in test_3
    self.assertEqual(self.relobj.obj, self.obj)
AssertionError: <app.models.Obj object at 0x7f579e2afe10> != <Obj 1 at id 7f579e2afc18>

----------------------------------------------------------------------
Ran 3 tests in 0.004s

FAILED (failures=1)
Destroying test database for alias 'default'...
}}}

The problem seems to be within the `Obj` creation in `test_2` which assigns `self.relobj` / `cls.relobj` the instance of the newly created object that couldn't be saved.

I'm on Django 1.9.dev20150818235245.

I know that I could use `refresh_from_db()`, but that seems counter productive, given the intention of `setUpTestData()`. Using `setUp()` instead of `setUpTestData()` also works."	Cleanup/optimization	closed	Documentation	1.8	Normal	fixed			Accepted	1	0	0	0	1	0