nl: use value parser for "--number-format"

tests/by-util/test_nl.rs

@@ -1,3 +1,4 @@
+// spell-checker:ignore ninvalid
 use crate::common::util::TestScenario;
 
 #[test]
@@ -78,3 +79,46 @@ fn test_no_renumber() {
         new_ucmd!().arg(arg).succeeds();
     }
 }
+
+#[test]
+fn test_number_format_ln() {
+    for arg in ["-nln", "--number-format=ln"] {
+        new_ucmd!()
+            .arg(arg)
+            .pipe_in("test")
+            .succeeds()
+            .stdout_is("1     \ttest\n");
+    }
+}
+
+#[test]
+fn test_number_format_rn() {
+    for arg in ["-nrn", "--number-format=rn"] {
+        new_ucmd!()
+            .arg(arg)
+            .pipe_in("test")
+            .succeeds()
+            .stdout_is("     1\ttest\n");
+    }
+}
+
+#[test]
+fn test_number_format_rz() {
+    for arg in ["-nrz", "--number-format=rz"] {
+        new_ucmd!()
+            .arg(arg)
+            .pipe_in("test")
+            .succeeds()
+            .stdout_is("000001\ttest\n");
+    }
+}
+
+#[test]
+fn test_invalid_number_format() {
+    for arg in ["-ninvalid", "--number-format=invalid"] {
+        new_ucmd!()
+            .arg(arg)
+            .fails()
+            .stderr_contains("invalid value 'invalid'");
+    }
+}