Add a documentation example on read only database tests. Refs #418.

Author: pelme

docs/database.rst

@@ -426,3 +426,28 @@ Put this in ``conftest.py``::
                 INSERT INTO theapp_item (name) VALUES ('created from a sql script');
                 ''')
 
+
+Use a read only database
+""""""""""""""""""""""""
+
+You can replace the ordinary `django_db_setup` to completely avoid database
+creation/migrations. If you have no need for rollbacks or truncating tables,
+you can simply avoid blocking the database and use it directly. When using this
+method you must ensure that your tests do not change the database state.
+
+
+Put this in ``conftest.py``::
+
+    import pytest
+
+
+    @pytest.fixture(scope='session')
+    def django_db_setup():
+        """Avoid creating/setting up the test database"""
+        pass
+
+
+    @pytest.fixture
+    def db_access_without_rollback_and_truncate(request, django_db_setup, django_db_blocker):
+        django_db_blocker.unblock()
+        request.addfinalizer(django_db_blocker.restore)