fix: keep idle heartbeat test assertions meaningful

Author: mykaul

tests/integration/standard/test_cluster.py

@@ -771,6 +771,7 @@ def test_idle_heartbeat(self):
         # make sure requests were sent on all connections
         # Note: connections can be replaced in shard-aware environments, so we skip
         # connections that weren't present in the initial snapshot
+        validated_connections = 0
         for c in connections:
             conn_id = id(c)
             if conn_id not in connection_request_ids:
@@ -780,6 +781,9 @@ def test_idle_heartbeat(self):
             expected_ids.rotate(-1)
             with c.lock:
                 assertListEqual(list(c.request_ids), list(expected_ids))
+            validated_connections += 1
+
+        assert validated_connections > 0
 
         # assert idle status
         assert all(c.is_idle for c in connections)