diff --git a/tests/router_unit_tests/test_router_index_management.py b/tests/router_unit_tests/test_router_index_management.py
index 04ea9214991..63f9d118349 100644
--- a/tests/router_unit_tests/test_router_index_management.py
+++ b/tests/router_unit_tests/test_router_index_management.py
@@ -177,3 +177,11 @@ class TestRouterIndexManagement:
         # Verify: New entry is added
         assert "claude-3" in router.model_name_to_deployment_indices
         assert router.model_name_to_deployment_indices["claude-3"] == [0]
+
+    def test_model_names_is_set(self):
+        """Verify that model_names uses a set for O(1) lookups, not a list (O(n))"""
+        router = Router(model_list=[])
+        
+        assert isinstance(router.model_names, set), (
+            f"model_names should be a set for O(1) lookups, but got {type(router.model_names)}"
+        )