Fix deepcopy on EmbeddedDocument

tests/document/test_instance.py

@@ -3,6 +3,7 @@ import pickle
 import unittest
 import uuid
 import weakref
+from copy import deepcopy
 from datetime import datetime
 
 import bson
@@ -78,6 +79,14 @@ class TestDocumentInstance(MongoDBTestCase):
         else:
             assert field._instance == instance
 
+    def test_deepcopy(self):
+        """Ensure that the _instance attribute on EmbeddedDocument exists after a deepcopy"""
+
+        doc = self.Job()
+        assert doc._instance is None
+        copied = deepcopy(doc)
+        assert copied._instance is None
+
     def test_capped_collection(self):
         """Ensure that capped collections work properly."""