Fix MongoTestCase and add test for it

mongoengine/django/tests.py

@@ -1,16 +1,9 @@
 #coding: utf-8
 
+from unittest import TestCase
+
 from mongoengine import connect
 from mongoengine.connection import get_db
-from mongoengine.python_support import PY3
-
-try:
-    from django.test import TestCase
-except Exception as err:
-    if PY3:
-        from unittest import TestCase
-    else:
-        raise err
 
 
 class MongoTestCase(TestCase):
@@ -28,20 +21,11 @@ class MongoTestCase(TestCase):
         self.db = get_db()
         super(MongoTestCase, self).__init__(methodName)
 
-    def _post_teardown(self):
-        super(MongoTestCase, self)._post_teardown()
+    def dropCollections(self):
         for collection in self.db.collection_names():
             if collection == 'system.indexes':
                 continue
             self.db.drop_collection(collection)
 
-    # prevent standard db init
-
-    def _databases_names(self, *args, **kwargs):
-        return []
-
-    def _fixture_setup(self):
-        pass
-
-    def _fixture_teardown(self):
-        pass
+    def tearDown(self):
+        self.dropCollections()