Mark endpoints in zone as property attribute

Change-Id: I2974c47eebd82bb551c2c01c699ab6c69b28b754

rsd_lib/resources/v2_1/fabric/zone.py

@@ -63,13 +63,23 @@ class Zone(base.ResourceBase):
         super(Zone, self).__init__(connector, identity,
                                    redfish_version)
 
-    def get_endpoints(self):
+    @property
+    def endpoints(self):
         """Return a list of Endpoints present in the Zone
 
-        :returns: A list of Endpoint objects
+        It is calculated once when it is queried for the first time. On
+        refresh, this property is reset.
         """
-        return [endpoint.Endpoint(self._conn, id_, self.redfish_version) for
-                id_ in self.links.endpoint_identities]
+        if self._endpoints is None:
+            self._endpoints = [
+                endpoint.Endpoint(self._conn, id_, self.redfish_version)
+                for id_ in self.links.endpoint_identities]
+
+        return self._endpoints
+
+    def refresh(self):
+        super(Zone, self).refresh()
+        self._endpoints = None
 
     def update(self, endpoints):
         """Add or remove Endpoints from a Zone

rsd_lib/tests/unit/resources/v2_1/fabric/test_zone.py

@@ -48,14 +48,54 @@ class ZoneTestCase(testtools.TestCase):
         self.assertEqual('Enabled', self.zone_inst.status.state)
         self.assertEqual('OK', self.zone_inst.status.health)
 
-    def test_get_endpoints(self):
+    def test_endpoints(self):
+        # check for the underneath variable value
+        self.assertIsNone(self.zone_inst._endpoints)
+        # | GIVEN |
         self.conn.get.return_value.json.reset_mock()
         with open('rsd_lib/tests/unit/json_samples/v2_1/'
                   'endpoint.json', 'r') as f:
             self.conn.get.return_value.json.return_value = json.loads(f.read())
-        endpoints = self.zone_inst.get_endpoints()
-        self.assertEqual('NVMeDrivePF1', endpoints[0].identity)
-        self.assertEqual(2, len(endpoints))
+        # | WHEN |
+        actual_endpoints = self.zone_inst.endpoints
+        # | THEN |
+        self.assertEqual('NVMeDrivePF1', actual_endpoints[0].identity)
+        self.assertEqual(2, len(actual_endpoints))
+        self.conn.get.return_value.json.assert_called_with()
+
+        # reset mock
+        self.conn.get.return_value.json.reset_mock()
+        # | WHEN & THEN |
+        # tests for same object on invoking subsequently
+        self.assertIs(actual_endpoints,
+                      self.zone_inst.endpoints)
+        self.conn.get.return_value.json.assert_not_called()
+
+    def test_endpoints_on_refresh(self):
+        # | GIVEN |
+        with open('rsd_lib/tests/unit/json_samples/v2_1/'
+                  'endpoint.json', 'r') as f:
+            self.conn.get.return_value.json.return_value = json.loads(f.read())
+        # | WHEN & THEN |
+        self.assertEqual('NVMeDrivePF1', self.zone_inst.endpoints[0].identity)
+        self.assertEqual(2, len(self.zone_inst.endpoints))
+
+        # On refreshing the fabric instance...
+        with open('rsd_lib/tests/unit/json_samples/v2_1/'
+                  'zone.json', 'r') as f:
+            self.conn.get.return_value.json.return_value = json.loads(f.read())
+        self.zone_inst.refresh()
+
+        # | WHEN & THEN |
+        self.assertIsNone(self.zone_inst._endpoints)
+
+        # | GIVEN |
+        with open('rsd_lib/tests/unit/json_samples/v2_1/'
+                  'endpoint.json', 'r') as f:
+            self.conn.get.return_value.json.return_value = json.loads(f.read())
+        # | WHEN & THEN |
+        self.assertEqual('NVMeDrivePF1', self.zone_inst.endpoints[0].identity)
+        self.assertEqual(2, len(self.zone_inst.endpoints))
 
     def test_update(self):
         self.zone_inst.update(