SIENTIAPDE-1445

Invert startTime and endTime parameters in PIWebAPIClient to ensure descending order results. Update tests to verify parameter handling and use pytest.approx for floating-point comparisons.

scouter/utils/clients/pi_web_api_client.py

@@ -287,15 +287,18 @@ class PIWebAPIClient(SientiaMonitoring):
 
         # Build query parameters with WebIds (filtering out None values)
         params: list[tuple[str, str]] = [('webid', web_id['webid']) for web_id in web_ids.values()]
+        # Invert startTime and endTime to get descending order (most recent first)
+        # PI Web API returns descending order when endTime < startTime
         params.extend(
             [
-                ('startTime', start_time),
-                ('endtime', end_time),
+                ('startTime', end_time),  # Use end_time as startTime (inverted)
+                ('endtime', start_time),  # Use start_time as endTime (inverted)
                 ('selectedFields', 'Items.Name;Items.Items.Timestamp;Items.Items.Value'),
             ]
         )
 
-        params.append(('maxCount', str(max_count)))
+        if max_count is not None:
+            params.append(('maxCount', str(max_count)))
 
         data = await self._curl_get_json(
             url=url,