ReferenceField now store ObjectId's by default rather than DBRef (#290)

tests/migration/convert_to_new_inheritance_model.py

@@ -0,0 +1,51 @@
+# -*- coding: utf-8 -*-
+import unittest
+
+from mongoengine import Document, connect
+from mongoengine.connection import get_db
+from mongoengine.fields import StringField
+
+__all__ = ('ConvertToNewInheritanceModel', )
+
+
+class ConvertToNewInheritanceModel(unittest.TestCase):
+
+    def setUp(self):
+        connect(db='mongoenginetest')
+        self.db = get_db()
+
+    def tearDown(self):
+        for collection in self.db.collection_names():
+            if 'system.' in collection:
+                continue
+            self.db.drop_collection(collection)
+
+    def test_how_to_convert_to_the_new_inheritance_model(self):
+        """Demonstrates migrating from 0.7 to 0.8
+        """
+
+        # 1. Declaration of the class
+        class Animal(Document):
+            name = StringField()
+            meta = {
+                'allow_inheritance': True,
+                'indexes': ['name']
+            }
+
+        # 2. Remove _types
+        collection = Animal._get_collection()
+        collection.update({}, {"$unset": {"_types": 1}}, multi=True)
+
+        # 3. Confirm extra data is removed
+        count = collection.find({'_types': {"$exists": True}}).count()
+        self.assertEqual(0, count)
+
+        # 4. Remove indexes
+        info = collection.index_information()
+        indexes_to_drop = [key for key, value in info.iteritems()
+                           if '_types' in dict(value['key'])]
+        for index in indexes_to_drop:
+            collection.drop_index(index)
+
+        # 5. Recreate indexes
+        Animal.ensure_indexes()