Fixed #35660 -- Made serialized_rollback and fixture data available in TransactionTestCase.setUpClass().

tests/migration_test_data_persistence/tests.py

@@ -1,3 +1,4 @@
+from django.core.management import call_command
 from django.test import TestCase, TransactionTestCase
 
 from .models import Book
@@ -19,6 +20,26 @@ class MigrationDataPersistenceTestCase(TransactionTestCase):
         )
 
 
+class MigrationDataPersistenceClassSetup(TransactionTestCase):
+    """
+    Data loaded in migrations is available during class setup if
+    TransactionTestCase.serialized_rollback = True.
+    """
+
+    available_apps = ["migration_test_data_persistence"]
+    serialized_rollback = True
+
+    @classmethod
+    def setUpClass(cls):
+        # Simulate another TransactionTestCase having just torn down.
+        call_command("flush", verbosity=0, interactive=False)
+        super().setUpClass()
+        cls.book = Book.objects.first()
+
+    def test_data_available_in_class_setup(self):
+        self.assertIsInstance(self.book, Book)
+
+
 class MigrationDataNormalPersistenceTestCase(TestCase):
     """
     Data loaded in migrations is available on TestCase