From 64420ea54f169cc9078ae1d9673a35b88a7bd67d Mon Sep 17 00:00:00 2001
From: SaJH <wogur981208@gmail.com>
Date: Tue, 26 Aug 2025 02:58:44 +0900
Subject: [PATCH] Fixed #35548 -- Fixed data leakage when setUpTestData() fails
 without transaction support.

Signed-off-by: SaJH <wogur981208@gmail.com>
---
 django/test/testcases.py          |  7 ++++++-
 tests/test_utils/test_testcase.py | 33 +++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/django/test/testcases.py b/django/test/testcases.py
index 5f0c819815..cd6480ed6d 100644
--- a/django/test/testcases.py
+++ b/django/test/testcases.py
@@ -7,7 +7,7 @@ import sys
 import threading
 import unittest
 from collections import Counter
-from contextlib import contextmanager
+from contextlib import contextmanager, suppress
 from copy import copy, deepcopy
 from difflib import get_close_matches
 from functools import wraps
@@ -1153,6 +1153,11 @@ class TransactionTestCase(SimpleTestCase):
         try:
             cls._fixture_setup()
         except Exception:
+            # Attempt to teardown fixtures on exception during setup as
+            # _post_teardown won't be triggered to cleanup state when an
+            # an exception is surfaced to SimpleTestCase._pre_setup.
+            with suppress(Exception):
+                cls("setUp")._fixture_teardown()
             if cls.available_apps is not None:
                 apps.unset_available_apps()
                 setting_changed.send(
diff --git a/tests/test_utils/test_testcase.py b/tests/test_utils/test_testcase.py
index 866e0dccc6..fcbd8c6da6 100644
--- a/tests/test_utils/test_testcase.py
+++ b/tests/test_utils/test_testcase.py
@@ -1,5 +1,6 @@
 import pickle
 from functools import wraps
+from unittest.mock import patch
 
 from django.db import IntegrityError, connections, transaction
 from django.test import TestCase, skipUnlessDBFeature
@@ -168,3 +169,35 @@ class SetupTestDataIsolationTests(TestCase):
         self.assertEqual(self.car.name, "Volkswagen Beetle")
         self.car.name = "Volkswagen Coccinelle"
         self.car.save()
+
+
+class SetupTestDataExceptionTest(TestCase):
+    def test_cleanup_on_setup_exception_without_transactions(self):
+        with patch.object(
+            connections["default"].features, "supports_transactions", False
+        ):
+
+            class FailingSetupTestCase(TestCase):
+                @classmethod
+                def setUpTestData(cls):
+                    Car.objects.create(name="Should be cleaned up")
+                    raise ValueError("Simulated exception in setUpTestData")
+
+                def test_dummy(self):
+                    pass
+
+            test_instance = FailingSetupTestCase("test_dummy")
+
+            initial_count = Car.objects.count()
+
+            with self.assertRaises(ValueError):
+                test_instance._pre_setup()
+
+            final_count = Car.objects.count()
+
+            self.assertEqual(
+                initial_count,
+                final_count,
+                "Data was not cleaned up after setUpTestData exception. "
+                f"Cars before: {initial_count}, after: {final_count}",
+            )