install: add test to set owner to nonexistent userid

Author: zhw2101024

tests/by-util/test_install.rs

@@ -1764,3 +1764,18 @@ fn test_install_from_stdin() {
     assert!(at.file_exists(target));
     assert_eq!(at.read(target), test_string);
 }
+
+#[test]
+#[cfg(unix)]
+fn test_install_set_owner_nonexistent_userid() {
+    if let Ok(result) = run_ucmd_as_root(&ts, args) {
+        result.success();
+        assert!(at.file_exists(target));
+
+        let metadata = fs::metadata(at.plus(target)).unwrap();
+        assert_eq!(metadata.uid(), expected_uid);
+        assert_eq!(metadata.gid(), expected_gid);
+    } else {
+        print!("Test skipped; requires root user");
+    }
+}