Index: tests/dg_valves_test_observer.py
===================================================================
diff -u
--- tests/dg_valves_test_observer.py	(revision 0)
+++ tests/dg_valves_test_observer.py	(revision 0ef481abcfe4a92ef0e35aa3397f931953ce7a0e)
@@ -0,0 +1,74 @@
+###########################################################################
+#
+#  Copyright (c) 2019-2020 Diality Inc. - All Rights Reserved.
+#
+#  THIS CODE MAY NOT BE COPIED OR REPRODUCED IN ANY FORM, IN PART OR IN
+#  WHOLE, WITHOUT THE EXPLICIT PERMISSION OF THE COPYRIGHT OWNER.
+#
+#  @file dg_valves_test1.py
+#
+#  @date 01-June-2020
+#  @author S. Cheung
+#
+#  @brief This development test script exercises the DG valves states in \n
+#  single and batch modes
+#
+############################################################################
+
+import sys
+sys.path.append("..")
+from dialin.dg.dialysate_generator import DG
+from datetime import datetime, timedelta
+from dialin.utils.base import AbstractObserver
+import time
+
+
+class Observer(AbstractObserver):
+    def __init__(self, max_observations=20):
+        self.ready = False
+        self.timedelta_in_ms = 0
+        self.timestamps = []
+        self.max_observations = max_observations
+        self.observations = 0
+        self.run = True
+        self.deltas = []
+
+    def update(self, result):
+        self.observations += 1
+
+        if result.get('datetime', False):
+            self.timestamps.append(datetime.strptime(result["datetime"], "%m.%d.%Y_%I.%M.%S.%f"))
+
+            max_publish_rate = 500
+            tolerance = 0.1
+            max_publish_rate_after_tolerance = max_publish_rate * (1+tolerance)
+            if len(self.timestamps) > 1:
+                delta = self.timestamps[-1] - self.timestamps[-2]
+                self.deltas.append(delta.microseconds*10**-3)
+                max_delta = timedelta(seconds = max_publish_rate_after_tolerance*10**(-3))
+                print(delta)
+                assert(delta <= max_delta)
+
+        if self.observations >= self.max_observations:
+            self.run = False
+
+
+def test_monitor_dg_valve_state_rate_1():
+    """
+    Test if DG monitors valve states within every 500 ms
+    """
+    dg = DG()
+
+    valves_observer = Observer()
+    dg.valves.attach(valves_observer)
+
+    while valves_observer.run:
+        time.sleep(0.010)
+
+    # print("DG Valve State Updates (ms):")
+    # for ms in valves_observer.deltas:
+    #     print(ms)
+
+
+if __name__ == "__main__":
+    test_monitor_dg_valve_state_rate_1()