tests/kill: test old form args with signal name

Add two tests of the old form signal arg using the signal name instead
of the number.

Bonus: add a test for the new form but with the prefix SIG-

tests/by-util/test_kill.rs

@@ -104,6 +104,26 @@ fn test_kill_with_signal_number_old_form() {
     assert_eq!(target.wait_for_signal(), Some(9));
 }
 
+#[test]
+fn test_kill_with_signal_name_old_form() {
+    let mut target = Target::new();
+    new_ucmd!()
+        .arg("-KILL")
+        .arg(format!("{}", target.pid()))
+        .succeeds();
+    assert_eq!(target.wait_for_signal(), Some(libc::SIGKILL));
+}
+
+#[test]
+fn test_kill_with_signal_prefixed_name_old_form() {
+    let mut target = Target::new();
+    new_ucmd!()
+        .arg("-SIGKILL")
+        .arg(format!("{}", target.pid()))
+        .succeeds();
+    assert_eq!(target.wait_for_signal(), Some(libc::SIGKILL));
+}
+
 #[test]
 fn test_kill_with_signal_number_new_form() {
     let mut target = Target::new();
@@ -125,3 +145,14 @@ fn test_kill_with_signal_name_new_form() {
         .succeeds();
     assert_eq!(target.wait_for_signal(), Some(libc::SIGKILL));
 }
+
+#[test]
+fn test_kill_with_signal_prefixed_name_new_form() {
+    let mut target = Target::new();
+    new_ucmd!()
+        .arg("-s")
+        .arg("SIGKILL")
+        .arg(format!("{}", target.pid()))
+        .succeeds();
+    assert_eq!(target.wait_for_signal(), Some(libc::SIGKILL));
+}