Fixed #22487: Don't flush out data from before normal TestCases

django/core/management/commands/migrate.py

@@ -129,6 +129,18 @@ class Command(BaseCommand):
         else:
             created_models = []
 
+        # The test runner requires us to flush after a syncdb but before migrations,
+        # so do that here.
+        if options.get("test_flush", False):
+            call_command(
+                'flush',
+                verbosity=max(self.verbosity - 1, 0),
+                interactive=False,
+                database=db,
+                reset_sequences=False,
+                inhibit_post_migrate=True,
+            )
+
         # Migrate!
         if self.verbosity >= 1:
             self.stdout.write(self.style.MIGRATE_HEADING("Running migrations:"))

django/db/backends/creation.py

@@ -380,6 +380,7 @@ class BaseDatabaseCreation(object):
             interactive=False,
             database=self.connection.alias,
             test_database=True,
+            test_flush=True,
         )
 
         # We then serialize the current state of the database into a string
@@ -389,14 +390,6 @@ class BaseDatabaseCreation(object):
         if serialize:
             self.connection._test_serialized_contents = self.serialize_db_to_string()
 
-        # Finally, we flush the database to clean
-        call_command(
-            'flush',
-            verbosity=max(verbosity - 1, 0),
-            interactive=False,
-            database=self.connection.alias
-        )
-
         call_command('createcachetable', database=self.connection.alias)
 
         # Ensure a connection for the side effect of initializing the test database.

tests/migration_test_data_persistence/tests.py

-from django.test import TransactionTestCase
+from django.test import TransactionTestCase, TestCase
 from .models import Book
 
 
 class MigrationDataPersistenceTestCase(TransactionTestCase):
     """
     Tests that data loaded in migrations is available if we set
-    serialized_rollback = True.
+    serialized_rollback = True on TransactionTestCase
     """
 
     available_apps = ["migration_test_data_persistence"]
@@ -18,16 +18,13 @@ class MigrationDataPersistenceTestCase(TransactionTestCase):
         )
 
 
-class MigrationDataNoPersistenceTestCase(TransactionTestCase):
+class MigrationDataNormalPersistenceTestCase(TestCase):
     """
-    Tests the failure case
+    Tests that data loaded in migrations is available on TestCase
     """
 
-    available_apps = ["migration_test_data_persistence"]
-    serialized_rollback = False
-
-    def test_no_persistence(self):
+    def test_persistence(self):
         self.assertEqual(
             Book.objects.count(),
-            0,
+            1,
         )