test(cksum): Add test for ignore-missing standard input

Author: RenjiSann

tests/by-util/test_cksum.rs

@@ -2755,6 +2755,21 @@ mod gnu_cksum_c {
             .stderr_contains("CHECKSUMS-missing: no file was verified");
     }
 
+    #[test]
+    fn test_ignore_missing_stdin() {
+        let scene = make_scene_with_checksum_missing();
+
+        scene
+            .ucmd()
+            .arg("--ignore-missing")
+            .arg("--check")
+            .pipe_in_fixture("CHECKSUMS-missing")
+            .fails()
+            .stdout_does_not_contain("nonexistent: No such file or directory")
+            .stdout_does_not_contain("nonexistent: FAILED open or read")
+            .stderr_contains("'standard input': no file was verified");
+    }
+
     #[test]
     fn test_status_and_warn() {
         let scene = make_scene_with_checksum_missing();