Fixed #25251 -- Made data migrations available in TransactionTestCase.

django/test/testcases.py

@@ -928,6 +928,16 @@ def _fixture_teardown(self):
                          allow_cascade=self.available_apps is not None,
                          inhibit_post_migrate=inhibit_post_migrate)
 
+            # If there was some initial data from migrated apps, restore them for the next test.
+            if self.serialized_rollback and hasattr(connections[db_name], "_test_serialized_contents"):
+                if self.available_apps is not None:
+                    apps.unset_available_apps()
+                connections[db_name].creation.deserialize_db_from_string(
+                    connections[db_name]._test_serialized_contents
+                )
+                if self.available_apps is not None:
+                    apps.set_available_apps(self.available_apps)
+
     def assertQuerysetEqual(self, qs, values, transform=repr, ordered=True, msg=None):
         items = six.moves.map(transform, qs)
         if not ordered:

docs/releases/1.10.txt

@@ -600,6 +600,17 @@ You can check if your database has any of the removed hashers like this::
     # Unsalted MD5 passwords might not have an 'md5$$' prefix:
     User.objects.filter(password__length=32)
 
+``TransactionTestCase`` serialized data loading
+-----------------------------------------------
+
+Initial data migrations are now loaded in ``TransactionTestCase`` at the end of
+the test, after the database flush.
+In older versions, these data were loaded at the beginning of the test, but
+this behavior was preventing ``--keepdb`` option to work properly (the
+database was empty at the end of the whole test suite).
+It shouldn't have any impact on your test suite if you have not customized
+``TransactionTestCase`` internal logic.
+
 Miscellaneous
 -------------
 

docs/topics/testing/overview.txt

@@ -259,6 +259,13 @@ To prevent serialized data from being loaded twice, setting
 :data:`~django.db.models.signals.post_migrate` signal when flushing the test
 database.
 
+.. versionchanged:: 1.10
+
+Data are now loaded at the end of a ``TransactionTestCase``, after
+the database flush (it was previously loaded at the beginning of the test).
+This change makes ``--keepdb`` option work properly if your test suite
+contains ``TransactionTestCase`` tests.
+
 Other test conditions
 ---------------------
 

tests/test_utils/test_transactiontestcase.py

@@ -1,7 +1,46 @@
+import json
+
+from django.apps import apps
+from django.db import connections
 from django.test import TransactionTestCase, mock
 
+from .models import Car
+
+
+class TestSerializedContentMockMixin(object):
+    """
+    This mixin should be used every time we want to test something involving
+    TransactionTestCase and serialized_rollback = True option to avoid test dependencies.
+    We mock what would be serialized by Django after initial data migrations, and restore it
+    at the end of the test.
+    """
+    initial_data_migration = '[]'
+    _connections_test_serialized_content = {}
+
+    def _pre_setup(self):
+        for db_name in self._databases_names(include_mirrors=False):
+            self._connections_test_serialized_content[db_name] = connections[db_name]._test_serialized_contents
+            connections[db_name]._test_serialized_contents = self.initial_data_migration
+        super(TestSerializedContentMockMixin, self)._pre_setup()
+
+    def _post_teardown(self):
+        super(TestSerializedContentMockMixin, self)._post_teardown()
+        for db_name in self._databases_names(include_mirrors=False):
+            connections[db_name]._test_serialized_contents = self._connections_test_serialized_content[db_name]
+
+    @classmethod
+    def tearDownClass(cls):
+        super(TestSerializedContentMockMixin, cls).tearDownClass()
+
+        # Cleaning any data that has been created by our mixin class
+        # to not impact any other django suite test.
+        json_data = json.loads(cls.initial_data_migration)
+        for data in json_data:
+            Klass = apps.get_model(*data['model'].split('.'))
+            Klass.objects.get(pk=data['pk']).delete()
 
-class TestSerializedRollbackInhibitsPostMigrate(TransactionTestCase):
+
+class TestSerializedRollbackInhibitsPostMigrate(TestSerializedContentMockMixin, TransactionTestCase):
     """
     TransactionTestCase._fixture_teardown() inhibits the post_migrate signal
     for test classes with serialized_rollback=True.
@@ -26,3 +65,20 @@ def test(self, call_command):
             reset_sequences=False, inhibit_post_migrate=True,
             database='default', verbosity=0,
         )
+
+
+class TestDataConsistencyOnTearDown(TestSerializedContentMockMixin, TransactionTestCase):
+    """
+    Initial data should be recreated in TransactionTestCase._fixture_teardown()
+    after the database is flushed so it's available in all tests.
+    """
+    available_apps = ['test_utils']
+    serialized_rollback = True
+    initial_data_migration = '[{"model": "test_utils.car", "pk": 666, "fields": {"name": "K 2000"}}]'
+
+    def _post_teardown(self):
+        super(TestDataConsistencyOnTearDown, self)._post_teardown()
+        self.assertTrue(Car.objects.exists())
+
+    def test_that_should_be_the_only_one_in_this_test_case(self):
+        pass