tests: Add serialization test

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

tests/mav_frame_tests.rs

@@ -23,7 +23,7 @@ mod mav_frame_tests {
     ];
 
     #[test]
-    pub fn test_deser() {
+    pub fn test_deser_ser() {
         use mavlink::{common::MavMessage, MavFrame, MavlinkVersion};
         let frame = MavFrame::<MavMessage>::deser(MavlinkVersion::V2, HEARTBEAT_V2)
             .expect("failed to parse message");
@@ -31,6 +31,10 @@ mod mav_frame_tests {
         assert_eq!(frame.header, crate::test_shared::COMMON_MSG_HEADER);
         let heartbeat_msg = crate::test_shared::get_heartbeat_msg();
 
+        let mut buffer = [0u8; HEARTBEAT_V2.len()];
+        frame.ser(&mut buffer);
+        assert_eq!(buffer[..buffer.len() - 2], HEARTBEAT_V2[..buffer.len() - 2]);
+
         let msg = match frame.msg {
             MavMessage::HEARTBEAT(msg) => msg,
             _ => panic!("Decoded wrong message type"),