diff --git a/stun-types/src/message.rs b/stun-types/src/message.rs
index 9cd0ab5..7d69362 100644
--- a/stun-types/src/message.rs
+++ b/stun-types/src/message.rs
@@ -1841,10 +1841,21 @@ mod tests {
                 let mtype = MessageType::from_class_method(c, m);
                 assert_eq!(mtype.class(), c);
                 assert_eq!(mtype.method(), m);
+                let bytes = mtype.to_bytes();
+                let ptype = MessageType::from_bytes(&bytes).unwrap();
+                assert_eq!(mtype, ptype);
             }
         }
     }
 
+    #[test]
+    fn msg_type_not_stun() {
+        assert!(matches!(
+            MessageType::from_bytes(&[0xc0, 0x00]),
+            Err(StunParseError::NotStun)
+        ));
+    }
+
     #[test]
     fn msg_roundtrip() {
         let _log = crate::tests::test_init_log();
@@ -1937,6 +1948,22 @@ mod tests {
         }
     }
 
+    #[test]
+    fn write_into_short_destination() {
+        let _log = crate::tests::test_init_log();
+        let mut msg = Message::builder_request(BINDING);
+        let software = Software::new("s").unwrap();
+        msg.add_attribute(&software).unwrap();
+        let len = msg.byte_len();
+        let mut dest = vec![0; len - 1];
+        assert!(
+            matches!(msg.write_into(&mut dest), Err(StunWriteError::TooSmall {
+            expected,
+            actual,
+        }) if expected == len && actual == len - 1)
+        );
+    }
+
     #[test]
     fn add_duplicate_integrity() {
         let _log = crate::tests::test_init_log();
@@ -1993,6 +2020,22 @@ mod tests {
         }
     }
 
+    #[test]
+    fn add_raw_attribute_after_integrity() {
+        let _log = crate::tests::test_init_log();
+        for algorithm in [IntegrityAlgorithm::Sha1, IntegrityAlgorithm::Sha256] {
+            let credentials = ShortTermCredentials::new("secret".to_owned()).into();
+            let mut msg = Message::builder_request(BINDING);
+            msg.add_message_integrity(&credentials, algorithm).unwrap();
+            let software = Software::new("s").unwrap();
+            let raw = software.to_raw();
+            assert!(matches!(
+                msg.add_raw_attribute(raw),
+                Err(StunWriteError::MessageIntegrityExists)
+            ));
+        }
+    }
+
     #[test]
     fn add_integrity_after_fingerprint() {
         let _log = crate::tests::test_init_log();
@@ -2007,6 +2050,31 @@ mod tests {
         }
     }
 
+    #[test]
+    fn duplicate_add_attribute() {
+        let _log = crate::tests::test_init_log();
+        let mut msg = Message::builder_request(BINDING);
+        let software = Software::new("s").unwrap();
+        msg.add_attribute(&software).unwrap();
+        assert!(matches!(
+            msg.add_attribute(&software),
+            Err(StunWriteError::AttributeExists(ty)) if ty == Software::TYPE
+        ));
+    }
+
+    #[test]
+    fn duplicate_add_raw_attribute() {
+        let _log = crate::tests::test_init_log();
+        let mut msg = Message::builder_request(BINDING);
+        let software = Software::new("s").unwrap();
+        let raw = software.to_raw();
+        msg.add_raw_attribute(raw.clone()).unwrap();
+        assert!(matches!(
+            msg.add_raw_attribute(raw),
+            Err(StunWriteError::AttributeExists(ty)) if ty == Software::TYPE
+        ));
+    }
+
     #[test]
     fn duplicate_fingerprint() {
         let _log = crate::tests::test_init_log();
@@ -2132,6 +2200,19 @@ mod tests {
         ));
     }
 
+    #[test]
+    fn add_raw_attribute_after_fingerprint() {
+        let _log = crate::tests::test_init_log();
+        let mut msg = Message::builder_request(BINDING);
+        msg.add_fingerprint().unwrap();
+        let software = Software::new("s").unwrap();
+        let raw = software.to_raw();
+        assert!(matches!(
+            msg.add_raw_attribute(raw),
+            Err(StunWriteError::FingerprintExists)
+        ));
+    }
+
     #[test]
     fn parse_truncated_message_header() {
         let _log = crate::tests::test_init_log();
@@ -2263,6 +2344,17 @@ mod tests {
         msg.add_attribute(&integrity).unwrap();
     }
 
+    #[test]
+    #[should_panic(expected = "Use add_message_integrity() instead")]
+    fn builder_add_raw_attribute_integrity_panic() {
+        let _log = crate::tests::test_init_log();
+        let mut msg = Message::builder_request(BINDING);
+        let hmac = [2; 20];
+        let integrity = MessageIntegrity::new(hmac);
+        let raw = integrity.to_raw();
+        msg.add_raw_attribute(raw).unwrap();
+    }
+
     #[test]
     #[should_panic(expected = "Use add_message_integrity() instead")]
     fn builder_add_attribute_integrity_sha256_panic() {
@@ -2273,14 +2365,36 @@ mod tests {
         msg.add_attribute(&integrity).unwrap();
     }
 
+    #[test]
+    #[should_panic(expected = "Use add_message_integrity() instead")]
+    fn builder_add_raw_attribute_integrity_sha256_panic() {
+        let _log = crate::tests::test_init_log();
+        let mut msg = Message::builder_request(BINDING);
+        let hmac = [2; 16];
+        let integrity = MessageIntegritySha256::new(&hmac).unwrap();
+        let raw = integrity.to_raw();
+        msg.add_raw_attribute(raw).unwrap();
+    }
+
     #[test]
     #[should_panic(expected = "Use add_fingerprint() instead")]
     fn builder_add_attribute_fingerprint_panic() {
         let _log = crate::tests::test_init_log();
         let mut msg = Message::builder_request(BINDING);
         let fingerprint = [2; 4];
-        let integrity = Fingerprint::new(fingerprint);
-        msg.add_attribute(&integrity).unwrap();
+        let fingerprint = Fingerprint::new(fingerprint);
+        msg.add_attribute(&fingerprint).unwrap();
+    }
+
+    #[test]
+    #[should_panic(expected = "Use add_fingerprint() instead")]
+    fn builder_add_raw_attribute_fingerprint_panic() {
+        let _log = crate::tests::test_init_log();
+        let mut msg = Message::builder_request(BINDING);
+        let fingerprint = [2; 4];
+        let fingerprint = Fingerprint::new(fingerprint);
+        let raw = fingerprint.to_raw();
+        msg.add_raw_attribute(raw).unwrap();
     }
 
     #[test]