add test

Author: Jayce Fayne

src/lib.rs

@@ -1912,6 +1912,14 @@ mod tests {
         };
     }
 
+    #[test]
+    fn test_recursion_limit() {
+        let mail_filepath = "./tests/files/nested.eml";
+        let mail = std::fs::read(mail_filepath)
+            .expect(&format!("Unable to open the file [{}]", mail_filepath));
+        parse_mail(&mail).err().unwrap();
+    }
+
     #[test]
     fn test_body_content_encoding_with_multipart() {
         let mail_filepath = "./tests/files/test_email_01.txt";