diff --git a/src/metric-engine/src/test_util.rs b/src/metric-engine/src/test_util.rs
index 291c851865bd..79a523bb5758 100644
--- a/src/metric-engine/src/test_util.rs
+++ b/src/metric-engine/src/test_util.rs
@@ -310,12 +310,12 @@ mod test {
 
         let region_dir = "test_metric_region";
         // assert metadata region's dir
-        let metadata_region_dir = join_dir(&region_dir, METADATA_REGION_SUBDIR);
+        let metadata_region_dir = join_dir(region_dir, METADATA_REGION_SUBDIR);
         let exist = object_store.is_exist(&metadata_region_dir).await.unwrap();
         assert!(exist);
 
         // assert data region's dir
-        let data_region_dir = join_dir(&region_dir, DATA_REGION_SUBDIR);
+        let data_region_dir = join_dir(region_dir, DATA_REGION_SUBDIR);
         let exist = object_store.is_exist(&data_region_dir).await.unwrap();
         assert!(exist);