test: integration tests for label_set and timestamp

tests/fns.rs

@@ -83,7 +83,8 @@ rollup_tests!(
     stddev_over_time,
     stdvar_over_time,
     present_over_time,
-    last_over_time
+    last_over_time,
+    timestamp
 );
 
 #[tokio::test]
@@ -108,6 +109,7 @@ async fn mql_label_map() {
 
 #[cfg(feature = "metricsql")]
 label_tests!(
+    mql_label_set,
     mql_sort_by_label,
     mql_sort_by_label_desc,
     mql_sort_by_label_numeric,