diff --git a/lib/xos-synchronizer/tests/test_diffs.py b/lib/xos-synchronizer/tests/test_diffs.py
new file mode 100644
index 0000000..9e09c0f
--- /dev/null
+++ b/lib/xos-synchronizer/tests/test_diffs.py
@@ -0,0 +1,110 @@
+# Copyright 2017-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+from mock import patch, call, Mock, PropertyMock
+import json
+
+import os
+import sys
+
+test_path = os.path.abspath(os.path.dirname(os.path.realpath(__file__)))
+sync_lib_dir = os.path.join(test_path, "..", "xossynchronizer")
+xos_dir = os.path.join(test_path, "..", "..", "..", "xos")
+services_dir = os.path.join(xos_dir, "../../xos_services")
+
+class TestDiffs(unittest.TestCase):
+
+    """ These tests are for the mock modelaccessor, to make sure it behaves like the real one """
+
+    def setUp(self):
+
+        self.sys_path_save = sys.path
+        # Setting up the config module
+        from xosconfig import Config
+
+        config = os.path.join(test_path, "test_config.yaml")
+        Config.clear()
+        Config.init(config, "synchronizer-config-schema.yaml")
+        # END Setting up the config module
+
+        from xossynchronizer.mock_modelaccessor_build import (
+            build_mock_modelaccessor,
+        )
+
+        # FIXME this is to get jenkins to pass the tests, somehow it is running tests in a different order
+        # and apparently it is not overriding the generated model accessor
+        build_mock_modelaccessor(sync_lib_dir, xos_dir, services_dir, [])
+        import xossynchronizer.modelaccessor
+
+        # import all class names to globals
+        for (
+            k,
+            v,
+        ) in (
+            xossynchronizer.modelaccessor.model_accessor.all_model_classes.items()
+        ):
+            globals()[k] = v
+
+        self.log = Mock()
+
+    def tearDown(self):
+        sys.path = self.sys_path_save
+
+    def test_new_diff(self):
+        site = Site(name="mysite")
+
+        self.assertEqual(site.is_new, True)
+        self.assertEqual(site._dict, {"name": "mysite"})
+        self.assertEqual(site.diff, {})
+        self.assertEqual(site.changed_fields, ["name"])
+        self.assertEqual(site.has_field_changed("name"), False)
+        self.assertEqual(site.has_field_changed("login_base"), False)
+
+        site.login_base = "bar"
+
+        self.assertEqual(site._dict, {"login_base": "bar", "name": "mysite"})
+        self.assertEqual(site.diff, {"login_base": (None, "bar")})
+        self.assertIn("name", site.changed_fields)
+        self.assertIn("login_base", site.changed_fields)
+        self.assertEqual(site.has_field_changed("name"), False)
+        self.assertEqual(site.has_field_changed("login_base"), True)
+        self.assertEqual(site.get_field_diff("login_base"), (None, "bar"))
+
+    def test_existing_diff(self):
+        site = Site(name="mysite", login_base="foo")
+
+        # this is what would happen after saving and re-loading
+        site.is_new = False
+        site.id = 1
+        site._initial = site._dict
+
+        self.assertEqual(site.is_new, False)
+        self.assertEqual(site._dict, {"id": 1, "name": "mysite", "login_base": "foo"})
+        self.assertEqual(site.diff, {})
+        self.assertEqual(site.changed_fields, [])
+        self.assertEqual(site.has_field_changed("name"), False)
+        self.assertEqual(site.has_field_changed("login_base"), False)
+
+        site.login_base = "bar"
+
+        self.assertEqual(site._dict, {"id": 1, "login_base": "bar", "name": "mysite"})
+        self.assertEqual(site.diff, {"login_base": ("foo", "bar")})
+        self.assertIn("login_base", site.changed_fields)
+        self.assertEqual(site.has_field_changed("name"), False)
+        self.assertEqual(site.has_field_changed("login_base"), True)
+
+
+if __name__ == "__main__":
+    unittest.main()