Fix broken unit test cases caused by overflow issues. (Tencent#79)

src/connection/connection.rs

@@ -4694,7 +4694,7 @@ pub(crate) mod tests {
         assert!(!packets.is_empty());
         let packet = &mut packets[0].0;
         let packet_len = packet.len();
-        packet[packet_len - 1] += 1;
+        packet[packet_len - 1] = packet[packet_len - 1].wrapping_add(1);
 
         // Server recv a corrupted Handshake
         TestPair::conn_packets_in(&mut test_pair.server, packets)?;
@@ -5520,7 +5520,7 @@ pub(crate) mod tests {
 
         // Tamper dcid field of the OneRTT packet
         let (mut packet, info) = packets.pop().unwrap();
-        packet[1] = packet[1] + 1; // change first byte of dcid field
+        packet[1] = packet[1].wrapping_add(1); // change first byte of dcid field
 
         // Server drop the packet with unknown dcid
         assert!(test_pair.server.recv(&mut packet, &info).is_ok());

src/endpoint.rs

@@ -2010,7 +2010,7 @@ mod tests {
     }
 
     #[test]
-    fn handshake_with_packet_dupulication() -> Result<()> {
+    fn handshake_with_packet_duplication() -> Result<()> {
         let mut t = TestPair::new();
 
         let mut case_conf = CaseConf::default();