test: add change prompt args test

src/builtins/change_prompt.rs

@@ -34,3 +34,18 @@ impl Builtin for ChangePrompt {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_change_prompt_no_args() {
+        assert_ne!(ChangePrompt.execute(&mut BuiltinConfig::new(), vec![]), Ok(()))
+    }
+
+    #[test]
+    fn test_change_prompt_multiple_args() {
+        assert_eq!(ChangePrompt.execute(&mut BuiltinConfig::new(), vec!["1".to_string(), "2".to_string()]), Err(ShellError::ExecuteFailure("expected only one argument".to_string())))
+    }
+}