diff --git a/lib/xos-synchronizer/tests/test_run.py b/lib/xos-synchronizer/tests/test_run.py
new file mode 100644
index 0000000..f5815f2
--- /dev/null
+++ b/lib/xos-synchronizer/tests/test_run.py
@@ -0,0 +1,121 @@
+# 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 json
+import unittest
+from mock import patch
+import mock
+import pdb
+import networkx as nx
+
+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")
+
+ANSIBLE_FILE = "/tmp/payload_test"
+
+
+def run_fake_ansible_template(*args, **kwargs):
+    opts = args[1]
+    open(ANSIBLE_FILE, "w").write(json.dumps(opts))
+
+
+def get_ansible_output():
+    ansible_str = open(ANSIBLE_FILE).read()
+    return json.loads(ansible_str)
+
+
+class TestRun(unittest.TestCase):
+    def setUp(self):
+        self.sys_path_save = sys.path
+        self.cwd_save = os.getcwd()
+
+        config = os.path.join(test_path, "test_config.yaml")
+        from xosconfig import Config
+
+        Config.clear()
+        Config.init(config, "synchronizer-config-schema.yaml")
+
+        from xossynchronizer.mock_modelaccessor_build import (
+            build_mock_modelaccessor,
+        )
+
+        build_mock_modelaccessor(sync_lib_dir, xos_dir, services_dir=None, service_xprotos=[])
+
+        os.chdir(os.path.join(test_path, ".."))  # config references tests/model-deps
+
+        import xossynchronizer.event_loop
+
+        reload(xossynchronizer.event_loop)
+        import xossynchronizer.backend
+
+        reload(xossynchronizer.backend)
+        from xossynchronizer.modelaccessor import model_accessor
+
+        # import all class names to globals
+        for (k, v) in model_accessor.all_model_classes.items():
+            globals()[k] = v
+
+        b = xossynchronizer.backend.Backend()
+        steps_dir = Config.get("steps_dir")
+        self.steps = b.load_sync_step_modules(steps_dir)
+        self.synchronizer = xossynchronizer.event_loop.XOSObserver(self.steps)
+        try:
+            os.remove("/tmp/sync_ports")
+        except OSError:
+            pass
+        try:
+            os.remove("/tmp/delete_ports")
+        except OSError:
+            pass
+
+    def tearDown(self):
+        sys.path = self.sys_path_save
+        os.chdir(self.cwd_save)
+
+    @mock.patch(
+        "steps.sync_instances.syncstep.run_template",
+        side_effect=run_fake_ansible_template,
+    )
+    @mock.patch("xossynchronizer.event_loop.model_accessor")
+    def test_run_once(self, mock_run_template, mock_accessor, *_other_accessors):
+
+        pending_objects, pending_steps = self.synchronizer.fetch_pending()
+        pending_objects2 = list(pending_objects)
+
+        any_cs = next(
+            obj for obj in pending_objects if obj.leaf_model_name == "ControllerSlice"
+        )
+        any_instance = next(
+            obj for obj in pending_objects2 if obj.leaf_model_name == "Instance"
+        )
+
+        slice = Slice()
+        any_instance.slice = slice
+        any_cs.slice = slice
+
+        self.synchronizer.run_once()
+
+        sync_ports = open("/tmp/sync_ports").read()
+        delete_ports = open("/tmp/delete_ports").read()
+
+        self.assertIn("successful", sync_ports)
+        self.assertIn("successful", delete_ports)
+
+
+if __name__ == "__main__":
+    unittest.main()