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
35660	serialized_rollback fixture is not available in TransactionTestCase.setUpClass	Jacob Walls	Jacob Walls	"`serialized_rollback=True` allows subsequent `TransactionTestCase` classes to continue depending on the data created in the app's initial migration after a previous `TransactionTestCase` truncated tables.

By trial and error, I found that I couldn't depend on this emulated rollback during the `setUpClass()` phase, but rather during the `setUp()` phase only. This results in a difficult DX when debugging  `setUpClass()` failures in tests that pass in isolation, and resorting to `setUp()` (as I ultimately did) has a performance penalty.

`TestCase` loads fixtures before running `setUpClass()`. Can we explore letting `TransactionTestCase` do the same? I imagine the refactor involves implementing `TransactionTestCase.setUpClass()`.

Nothing in the docs advises that the emulated rollback is only available during certain parts of the test lifecycle, so at the very least I'd suggest a docs update. Happy to cross-post to forum if this isn't a ""bug"".


----

**Sample project**

models.py
{{{
from django.db import models

class MyModel(models.Model):
    flag = models.BooleanField()
}}}

migrations/0001_initial.py
{{{
# Generated by Django 4.2.15 on 2024-08-06 19:34

from django.db import migrations, models

def seed_data(apps, schema_editor):
    MyModel = apps.get_model(""fooapp"", ""MyModel"")
    MyModel.objects.create(flag=True)


class Migration(migrations.Migration):

    initial = True

    dependencies = []

    operations = [
        migrations.CreateModel(
            name=""MyModel"",
            fields=[
                (
                    ""id"",
                    models.BigAutoField(
                        auto_created=True,
                        primary_key=True,
                        serialize=False,
                        verbose_name=""ID"",
                    ),
                ),
                (""flag"", models.BooleanField()),
            ],
        ),
        migrations.RunPython(seed_data, migrations.RunPython.noop),
    ]
}}}

tests.py

{{{
from django.test import TransactionTestCase

from .models import MyModel

def depend_on_fixture():
    assert MyModel.objects.count()


class A(TransactionTestCase):
    serialized_rollback = True

    @classmethod
    def setUpClass(cls):
        depend_on_fixture()

    def test_a(self):
        pass


class B(TransactionTestCase):
    serialized_rollback = True

    @classmethod
    def setUpClass(cls):
        depend_on_fixture()

    def test_b(self):
        pass

}}}

Gives only one failure, which you'll miss if developing the tests in isolation:

{{{
======================================================================
ERROR: setUpClass (fooapp.tests.B)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""/Users/jwalls/foo/fooapp/tests.py"", line 25, in setUpClass
    depend_on_fixture()
  File ""/Users/jwalls/foo/fooapp/tests.py"", line 6, in depend_on_fixture
    assert MyModel.objects.count()
AssertionError

----------------------------------------------------------------------
Ran 1 test in 0.004s

FAILED (errors=1)
}}}
"	Bug	closed	Testing framework	4.2	Normal	fixed	rollback emulation setUpClass TransactionTestCase		Ready for checkin	1	0	0	0	0	0