diff --git a/src/common.rs b/src/common.rs
index df83537..070caeb 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -12,23 +12,16 @@ pub struct Stream<'a, S: 'a, IO: 'a> {
     io: &'a mut IO
 }
 
-pub trait CompleteIo<'a, S: Session, IO: Read + Write>: Read + Write {
+pub trait WriteTls<'a, S: Session, IO: Read + Write>: Read + Write {
     fn write_tls(&mut self) -> io::Result<usize>;
-    fn complete_io(&mut self) -> io::Result<(usize, usize)>;
 }
 
 impl<'a, S: Session, IO: Read + Write> Stream<'a, S, IO> {
     pub fn new(session: &'a mut S, io: &'a mut IO) -> Self {
         Stream { session, io }
     }
-}
 
-impl<'a, S: Session, IO: Read + Write> CompleteIo<'a, S, IO> for Stream<'a, S, IO> {
-    default fn write_tls(&mut self) -> io::Result<usize> {
-        self.session.write_tls(self.io)
-    }
-
-    fn complete_io(&mut self) -> io::Result<(usize, usize)> {
+    pub fn complete_io(&mut self) -> io::Result<(usize, usize)> {
         // fork from https://github.com/ctz/rustls/blob/master/src/session.rs#L161
 
         let until_handshaked = self.session.is_handshaking();
@@ -74,6 +67,32 @@ impl<'a, S: Session, IO: Read + Write> CompleteIo<'a, S, IO> for Stream<'a, S, I
     }
 }
 
+impl<'a, S: Session, IO: Read + Write> WriteTls<'a, S, IO> for Stream<'a, S, IO> {
+    default fn write_tls(&mut self) -> io::Result<usize> {
+        self.session.write_tls(self.io)
+    }
+}
+
+impl<'a, S: Session, IO: Read + AsyncWrite> WriteTls<'a, S, IO> for Stream<'a, S, IO> {
+    fn write_tls(&mut self) -> io::Result<usize> {
+        struct V<'a, IO: 'a>(&'a mut IO);
+
+        impl<'a, IO: AsyncWrite> WriteV for V<'a, IO> {
+            fn writev(&mut self, vbytes: &[&[u8]]) -> io::Result<usize> {
+                let mut vbytes = VecBuf::new(vbytes);
+                match self.0.write_buf(&mut vbytes) {
+                    Ok(Async::Ready(n)) => Ok(n),
+                    Ok(Async::NotReady) => Err(io::ErrorKind::WouldBlock.into()),
+                    Err(err) => Err(err)
+                }
+            }
+        }
+
+        let mut vecbuf = V(self.io);
+        self.session.writev_tls(&mut vecbuf)
+    }
+}
+
 impl<'a, S: Session, IO: Read + Write> Read for Stream<'a, S, IO> {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         while self.session.wants_read() {
@@ -102,28 +121,7 @@ impl<'a, S: Session, IO: Read + Write> io::Write for Stream<'a, S, IO> {
     }
 }
 
-impl<'a, S: Session, IO: Read + AsyncWrite> CompleteIo<'a, S, IO> for Stream<'a, S, IO> {
-    fn write_tls(&mut self) -> io::Result<usize> {
-        struct V<'a, IO: 'a>(&'a mut IO);
 
-        impl<'a, IO: AsyncWrite> WriteV for V<'a, IO> {
-            fn writev(&mut self, vbytes: &[&[u8]]) -> io::Result<usize> {
-                let mut vbytes = VecBuf::new(vbytes);
-                match self.0.write_buf(&mut vbytes) {
-                    Ok(Async::Ready(n)) => Ok(n),
-                    Ok(Async::NotReady) => Err(io::ErrorKind::WouldBlock.into()),
-                    Err(err) => Err(err)
-                }
-            }
-        }
-
-        let mut vecbuf = V(self.io);
-        self.session.writev_tls(&mut vecbuf)
-    }
-}
-
-
-// TODO test
 struct VecBuf<'a, 'b: 'a> {
     pos: usize,
     cur: usize,
@@ -153,14 +151,14 @@ impl<'a, 'b> Buf for VecBuf<'a, 'b> {
     fn advance(&mut self, cnt: usize) {
         let current = self.inner[self.pos].len();
         match (self.cur + cnt).cmp(&current) {
-            Ordering::Equal => {
-                if self.pos < self.inner.len() {
-                    self.pos += 1;
-                }
+            Ordering::Equal => if self.pos + 1 < self.inner.len() {
+                self.pos += 1;
                 self.cur = 0;
+            } else {
+                self.cur += cnt;
             },
             Ordering::Greater => {
-                if self.pos < self.inner.len() {
+                if self.pos + 1 < self.inner.len() {
                     self.pos += 1;
                 }
                 let remaining = self.cur + cnt - current;
@@ -180,3 +178,60 @@ impl<'a, 'b> Buf for VecBuf<'a, 'b> {
         len
     }
 }
+
+#[cfg(test)]
+mod test_vecbuf {
+    use super::*;
+
+    #[test]
+    fn test_fresh_cursor_vec() {
+        let mut buf = VecBuf::new(&[b"he", b"llo"]);
+
+        assert_eq!(buf.remaining(), 5);
+        assert_eq!(buf.bytes(), b"he");
+
+        buf.advance(2);
+
+        assert_eq!(buf.remaining(), 3);
+        assert_eq!(buf.bytes(), b"llo");
+
+        buf.advance(3);
+
+        assert_eq!(buf.remaining(), 0);
+        assert_eq!(buf.bytes(), b"");
+    }
+
+    #[test]
+    fn test_get_u8() {
+        let mut buf = VecBuf::new(&[b"\x21z", b"omg"]);
+        assert_eq!(0x21, buf.get_u8());
+    }
+
+    #[test]
+    fn test_get_u16() {
+        let mut buf = VecBuf::new(&[b"\x21\x54z", b"omg"]);
+        assert_eq!(0x2154, buf.get_u16_be());
+        let mut buf = VecBuf::new(&[b"\x21\x54z", b"omg"]);
+        assert_eq!(0x5421, buf.get_u16_le());
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_get_u16_buffer_underflow() {
+        let mut buf = VecBuf::new(&[b"\x21"]);
+        buf.get_u16_be();
+    }
+
+    #[test]
+    fn test_bufs_vec() {
+        let buf = VecBuf::new(&[b"he", b"llo"]);
+
+        let b1: &[u8] = &mut [0];
+        let b2: &[u8] = &mut [0];
+
+        let mut dst: [&IoVec; 2] =
+            [b1.into(), b2.into()];
+
+        assert_eq!(2, buf.bytes_vec(&mut dst[..]));
+    }
+}
diff --git a/src/tokio_impl.rs b/src/tokio_impl.rs
index 663d6ca..9f09705 100644
--- a/src/tokio_impl.rs
+++ b/src/tokio_impl.rs
@@ -2,7 +2,7 @@ use super::*;
 use tokio::prelude::*;
 use tokio::io::{ AsyncRead, AsyncWrite };
 use tokio::prelude::Poll;
-use common::{ Stream, CompleteIo };
+use common::Stream;
 
 
 impl<S: AsyncRead + AsyncWrite> Future for ConnectAsync<S> {