Add a simple UDP test

src/tcp.rs

@@ -1,3 +1,4 @@
+use std::fmt;
 use std::io::{self, ErrorKind, Read, Write};
 use std::mem;
 use std::net::{self, SocketAddr, Shutdown};
@@ -127,6 +128,12 @@ impl Iterator for NonblockingIter {
     }
 }
 
+impl fmt::Debug for TcpListener {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.listener.io().fmt(f)
+    }
+}
+
 impl Stream for TcpListener {
     type Item = Ready;
     type Error = io::Error;
@@ -335,6 +342,12 @@ impl<'a> Write for &'a TcpStream {
     }
 }
 
+impl fmt::Debug for TcpStream {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.source.io().fmt(f)
+    }
+}
+
 impl Stream for TcpStream {
     type Item = Ready;
     type Error = io::Error;