Add support for serialized rollback

Fix pytest-dev#329.

Author: aaugustin

docs/changelog.rst

@@ -10,6 +10,12 @@ Bug fixes
   Thanks to Will Harris for `the bug report
   <https://github.com/pytest-dev/pytest-django/issues/289>`_.
 
+Features
+^^^^^^^^
+* Add support for serialized rollback in transactional tests.
+  Thanks to Piotr Karkut for `the bug report
+  <https://github.com/pytest-dev/pytest-django/issues/329>`_.
+
 Features
 ^^^^^^^^
 * Added a new option `--migrations` to negate a default usage of

docs/helpers.rst

@@ -16,7 +16,7 @@ on what marks are and for notes on using_ them.
 ``pytest.mark.django_db`` - request database access
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-.. py:function:: pytest.mark.django_db([transaction=False])
+.. py:function:: pytest.mark.django_db([transaction=False, serialized_rollback=False])
 
    This is used to mark a test function as requiring the database. It
    will ensure the database is setup correctly for the test. Each test
@@ -38,6 +38,14 @@ on what marks are and for notes on using_ them.
      uses. When ``transaction=True``, the behavior will be the same as
      `django.test.TransactionTestCase`_
 
+   :type serialized_rollback: bool
+   :param serialized_rollback:
+     The ``serialized_rollback`` argument enables `rollback emulation`_.
+     After a `django.test.TransactionTestCase`_ runs, the database is
+     flushed, destroying data created in data migrations. This is the
+     default behavior of Django. Setting ``serialized_rollback=True``
+     tells Django to restore that data.
+
    .. note::
 
       If you want access to the Django database *inside a fixture*
@@ -54,6 +62,7 @@ on what marks are and for notes on using_ them.
      Test classes that subclass Python's ``unittest.TestCase`` need to have the
      marker applied in order to access the database.
 
+.. _rollback emulation: https://docs.djangoproject.com/en/stable/topics/testing/overview/#rollback-emulation
 .. _django.test.TestCase: https://docs.djangoproject.com/en/dev/topics/testing/overview/#testcase
 .. _django.test.TransactionTestCase: https://docs.djangoproject.com/en/dev/topics/testing/overview/#transactiontestcase
 
@@ -191,6 +200,16 @@ transaction support.  This is only required for fixtures which need
 database access themselves.  A test function would normally use the
 :py:func:`~pytest.mark.django_db` mark to signal it needs the database.
 
+``serialized_rollback``
+~~~~~~~~~~~~~~~~~~~~~~~
+
+When the ``transactional_db`` fixture is enabled, this fixture can be
+added to trigger `rollback emulation`_ and thus restores data created
+in data migrations after each transaction test.  This is only required
+for fixtures which need to enforce this behavior.  A test function
+would use :py:func:`~pytest.mark.django_db(serialized_rollback=True)`
+to request this behavior.
+
 ``live_server``
 ~~~~~~~~~~~~~~~
 
@@ -200,6 +219,12 @@ or by requesting it's string value: ``unicode(live_server)``.  You can
 also directly concatenate a string to form a URL: ``live_server +
 '/foo``.
 
+Since the live server and the tests run in different threads, they
+cannot share a database transaction. For this reason, ``live_server``
+depends on the ``transactional_db`` fixture. If tests depend on data
+created in data migrations, you should add the ``serialized_rollback``
+fixture.
+
 ``settings``
 ~~~~~~~~~~~~
 

pytest_django/fixtures.py

@@ -63,7 +63,8 @@ def teardown_database():
         request.addfinalizer(teardown_database)
 
 
-def _django_db_fixture_helper(transactional, request, _django_cursor_wrapper):
+def _django_db_fixture_helper(transactional, serialized_rollback,
+                              request, _django_cursor_wrapper):
     if is_django_unittest(request):
         return
 
@@ -83,6 +84,7 @@ def _django_db_fixture_helper(transactional, request, _django_cursor_wrapper):
 
     if django_case:
         case = django_case(methodName='__init__')
+        case.serialized_rollback = serialized_rollback
         case._pre_setup()
         request.addfinalizer(case._post_teardown)
 
@@ -115,7 +117,9 @@ def db(request, _django_db_setup, _django_cursor_wrapper):
             or 'live_server' in request.funcargnames:
         request.getfuncargvalue('transactional_db')
     else:
-        _django_db_fixture_helper(False, request, _django_cursor_wrapper)
+        _django_db_fixture_helper(
+            transactional=False, serialized_rollback=False,
+            request=request, _django_cursor_wrapper=_django_cursor_wrapper)
 
 
 @pytest.fixture(scope='function')
@@ -130,7 +134,23 @@ def transactional_db(request, _django_db_setup, _django_cursor_wrapper):
     database setup will behave as only ``transactional_db`` was
     requested.
     """
-    _django_db_fixture_helper(True, request, _django_cursor_wrapper)
+    # TODO -- is request.getfuncargvalue('serialized_rollback') enough
+    #         to add 'serialized_rollback' to request.funcargnames?
+    serialized_rollback = 'serialized_rollback' in request.funcargnames
+    _django_db_fixture_helper(transactional=True,
+                              serialized_rollback=serialized_rollback,
+                              request=request,
+                              _django_cursor_wrapper=_django_cursor_wrapper)
+
+
+@pytest.fixture(scope='function')
+def serialized_rollback(request):
+    """Enable serialized rollback after transaction test cases
+
+    This fixture only has an effect when the ``transactional_db``
+    fixture is active, which happen as a side-effect of requesting
+    ``live_server``.
+    """
 
 
 @pytest.fixture()

pytest_django/plugin.py

@@ -361,6 +361,8 @@ def _django_db_marker(request):
             request.getfuncargvalue('transactional_db')
         else:
             request.getfuncargvalue('db')
+        if marker.serialized_rollback:
+            request.getfuncargvalue('serialized_rollback')
 
 
 @pytest.fixture(autouse=True, scope='class')
@@ -559,8 +561,9 @@ def validate_django_db(marker):
     It checks the signature and creates the `transaction` attribute on
     the marker which will have the correct value.
     """
-    def apifun(transaction=False):
+    def apifun(transaction=False, serialized_rollback=False):
         marker.transaction = transaction
+        marker.serialized_rollback = serialized_rollback
     apifun(*marker.args, **marker.kwargs)