refactored deprecated pymongo methods in tests

- remove/count/add_user/insert
- added pymongo_support

tests/document/delta.py

@@ -3,16 +3,14 @@ import unittest
 
 from bson import SON
 from mongoengine import *
-from mongoengine.connection import get_db
-
-__all__ = ("DeltaTest",)
+from mongoengine.pymongo_support import list_collection_names
+from tests.utils import MongoDBTestCase
 
 
-class DeltaTest(unittest.TestCase):
+class DeltaTest(MongoDBTestCase):
 
     def setUp(self):
-        connect(db='mongoenginetest')
-        self.db = get_db()
+        super(DeltaTest, self).setUp()
 
         class Person(Document):
             name = StringField()
@@ -25,9 +23,7 @@ class DeltaTest(unittest.TestCase):
         self.Person = Person
 
     def tearDown(self):
-        for collection in self.db.collection_names():
-            if 'system.' in collection:
-                continue
+        for collection in list_collection_names(self.db):
             self.db.drop_collection(collection)
 
     def test_delta(self):