diff --git a/serde/src/bytes.rs b/serde/src/bytes.rs
index 84c30866..574a673d 100644
--- a/serde/src/bytes.rs
+++ b/serde/src/bytes.rs
@@ -65,7 +65,7 @@ impl<'a> ops::Deref for Bytes<'a> {
 
 impl<'a> ser::Serialize for Bytes<'a> {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: ser::Serializer
     {
         serializer.serialize_bytes(self.bytes)
@@ -168,7 +168,7 @@ mod bytebuf {
     }
 
     impl ser::Serialize for ByteBuf {
-        fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
             where S: ser::Serializer
         {
             serializer.serialize_bytes(self)
diff --git a/serde/src/ser/impls.rs b/serde/src/ser/impls.rs
index 4be35fc3..1d9205ab 100644
--- a/serde/src/ser/impls.rs
+++ b/serde/src/ser/impls.rs
@@ -69,6 +69,10 @@ use core::nonzero::{NonZero, Zeroable};
 use super::{
     Error,
     Serialize,
+    SerializeMap,
+    SerializeSeq,
+    SerializeStruct,
+    SerializeTuple,
     Serializer,
 };
 
@@ -81,7 +85,7 @@ macro_rules! impl_visit {
     ($ty:ty, $method:ident) => {
         impl Serialize for $ty {
             #[inline]
-            fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
                 where S: Serializer,
             {
                 serializer.$method(*self)
@@ -109,7 +113,7 @@ impl_visit!(char, serialize_char);
 
 impl Serialize for str {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         serializer.serialize_str(self)
@@ -119,7 +123,7 @@ impl Serialize for str {
 #[cfg(any(feature = "std", feature = "collections"))]
 impl Serialize for String {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         (&self[..]).serialize(serializer)
@@ -128,9 +132,11 @@ impl Serialize for String {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-impl<T> Serialize for Option<T> where T: Serialize {
+impl<T> Serialize for Option<T>
+    where T: Serialize
+{
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         match *self {
@@ -144,7 +150,7 @@ impl<T> Serialize for Option<T> where T: Serialize {
 
 impl<T> Serialize for PhantomData<T> {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         serializer.serialize_unit_struct("PhantomData")
@@ -158,14 +164,14 @@ impl<T> Serialize for [T]
     where T: Serialize,
 {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
-        let mut state = try!(serializer.serialize_seq(Some(self.len())));
+        let mut seq = try!(serializer.serialize_seq(Some(self.len())));
         for e in self {
-            try!(serializer.serialize_seq_elt(&mut state, e));
+            try!(seq.serialize_element(e));
         }
-        serializer.serialize_seq_end(state)
+        seq.end()
     }
 }
 
@@ -175,14 +181,14 @@ macro_rules! array_impls {
     ($len:expr) => {
         impl<T> Serialize for [T; $len] where T: Serialize {
             #[inline]
-            fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
                 where S: Serializer,
             {
-                let mut state = try!(serializer.serialize_seq_fixed_size($len));
+                let mut seq = try!(serializer.serialize_seq_fixed_size($len));
                 for e in self {
-                    try!(serializer.serialize_seq_elt(&mut state, e));
+                    try!(seq.serialize_element(e));
                 }
-                serializer.serialize_seq_end(state)
+                seq.end()
             }
         }
     }
@@ -229,7 +235,7 @@ impl<'a, I> Serialize for Iterator<I>
     where I: IntoIterator, <I as IntoIterator>::Item: Serialize
 {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         // FIXME: use specialization to prevent invalidating the object in case of clonable iterators?
@@ -241,11 +247,11 @@ impl<'a, I> Serialize for Iterator<I>
             (lo, Some(hi)) if lo == hi => Some(lo),
             _ => None,
         };
-        let mut state = try!(serializer.serialize_seq(size));
+        let mut seq = try!(serializer.serialize_seq(size));
         for e in iter {
-            try!(serializer.serialize_seq_elt(&mut state, e));
+            try!(seq.serialize_element(e));
         }
-        serializer.serialize_seq_end(state)
+        seq.end()
     }
 }
 
@@ -254,14 +260,14 @@ impl<'a, I> Serialize for Iterator<I>
 macro_rules! serialize_seq {
     () => {
         #[inline]
-        fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
             where S: Serializer,
         {
-            let mut state = try!(serializer.serialize_seq(Some(self.len())));
+            let mut seq = try!(serializer.serialize_seq(Some(self.len())));
             for e in self {
-                try!(serializer.serialize_seq_elt(&mut state, e));
+                try!(seq.serialize_element(e));
             }
-            serializer.serialize_seq_end(state)
+            seq.end()
         }
     }
 }
@@ -303,12 +309,16 @@ impl<T> Serialize for LinkedList<T>
 }
 
 #[cfg(any(feature = "std", feature = "collections"))]
-impl<T> Serialize for Vec<T> where T: Serialize {
+impl<T> Serialize for Vec<T>
+    where T: Serialize
+{
     serialize_seq!();
 }
 
 #[cfg(any(feature = "std", feature = "collections"))]
-impl<T> Serialize for VecDeque<T> where T: Serialize {
+impl<T> Serialize for VecDeque<T>
+    where T: Serialize
+{
     serialize_seq!();
 }
 
@@ -318,15 +328,15 @@ impl<A> Serialize for ops::Range<A>
           for<'a> &'a A: ops::Add<&'a A, Output = A>,
 {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         let len = iter::Step::steps_between(&self.start, &self.end, &A::one());
-        let mut state = try!(serializer.serialize_seq(len));
+        let mut seq = try!(serializer.serialize_seq(len));
         for e in self.clone() {
-            try!(serializer.serialize_seq_elt(&mut state, e));
+            try!(seq.serialize_element(e));
         }
-        serializer.serialize_seq_end(state)
+        seq.end()
     }
 }
 
@@ -334,7 +344,7 @@ impl<A> Serialize for ops::Range<A>
 
 impl Serialize for () {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         serializer.serialize_unit()
@@ -354,14 +364,14 @@ macro_rules! tuple_impls {
                 where $($T: Serialize),+
             {
                 #[inline]
-                fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+                fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
                     where S: Serializer,
                 {
-                    let mut state = try!(serializer.serialize_tuple($len));
+                    let mut tuple = try!(serializer.serialize_tuple($len));
                     $(
-                        try!(serializer.serialize_tuple_elt(&mut state, &self.$idx));
+                        try!(tuple.serialize_element(&self.$idx));
                     )+
-                    serializer.serialize_tuple_end(state)
+                    tuple.end()
                 }
             }
         )+
@@ -544,15 +554,15 @@ tuple_impls! {
 macro_rules! serialize_map {
     () => {
         #[inline]
-        fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+        fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
             where S: Serializer,
         {
-            let mut state = try!(serializer.serialize_map(Some(self.len())));
+            let mut map = try!(serializer.serialize_map(Some(self.len())));
             for (k, v) in self {
-                try!(serializer.serialize_map_key(&mut state, k));
-                try!(serializer.serialize_map_value(&mut state, v));
+                try!(map.serialize_key(k));
+                try!(map.serialize_value(v));
             }
-            serializer.serialize_map_end(state)
+            map.end()
         }
     }
 }
@@ -578,7 +588,7 @@ impl<K, V, H> Serialize for HashMap<K, V, H>
 
 impl<'a, T: ?Sized> Serialize for &'a T where T: Serialize {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         (**self).serialize(serializer)
@@ -587,7 +597,7 @@ impl<'a, T: ?Sized> Serialize for &'a T where T: Serialize {
 
 impl<'a, T: ?Sized> Serialize for &'a mut T where T: Serialize {
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         (**self).serialize(serializer)
@@ -595,9 +605,11 @@ impl<'a, T: ?Sized> Serialize for &'a mut T where T: Serialize {
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
-impl<T: ?Sized> Serialize for Box<T> where T: Serialize {
+impl<T: ?Sized> Serialize for Box<T>
+    where T: Serialize
+{
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         (**self).serialize(serializer)
@@ -605,9 +617,11 @@ impl<T: ?Sized> Serialize for Box<T> where T: Serialize {
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
-impl<T> Serialize for Rc<T> where T: Serialize, {
+impl<T> Serialize for Rc<T>
+    where T: Serialize
+{
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         (**self).serialize(serializer)
@@ -615,9 +629,11 @@ impl<T> Serialize for Rc<T> where T: Serialize, {
 }
 
 #[cfg(any(feature = "std", feature = "alloc"))]
-impl<T> Serialize for Arc<T> where T: Serialize, {
+impl<T> Serialize for Arc<T>
+    where T: Serialize
+{
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         (**self).serialize(serializer)
@@ -625,9 +641,11 @@ impl<T> Serialize for Arc<T> where T: Serialize, {
 }
 
 #[cfg(any(feature = "std", feature = "collections"))]
-impl<'a, T: ?Sized> Serialize for Cow<'a, T> where T: Serialize + ToOwned, {
+impl<'a, T: ?Sized> Serialize for Cow<'a, T>
+    where T: Serialize + ToOwned
+{
     #[inline]
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         (**self).serialize(serializer)
@@ -636,8 +654,13 @@ impl<'a, T: ?Sized> Serialize for Cow<'a, T> where T: Serialize + ToOwned, {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-impl<T, E> Serialize for Result<T, E> where T: Serialize, E: Serialize {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error> where S: Serializer {
+impl<T, E> Serialize for Result<T, E>
+    where T: Serialize,
+          E: Serialize
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
         match *self {
             Result::Ok(ref value) => {
                 serializer.serialize_newtype_variant("Result", 0, "Ok", value)
@@ -653,13 +676,13 @@ impl<T, E> Serialize for Result<T, E> where T: Serialize, E: Serialize {
 
 #[cfg(feature = "std")]
 impl Serialize for Duration {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         let mut state = try!(serializer.serialize_struct("Duration", 2));
-        try!(serializer.serialize_struct_elt(&mut state, "secs", self.as_secs()));
-        try!(serializer.serialize_struct_elt(&mut state, "nanos", self.subsec_nanos()));
-        serializer.serialize_struct_end(state)
+        try!(state.serialize_field("secs", self.as_secs()));
+        try!(state.serialize_field("nanos", self.subsec_nanos()));
+        state.end()
     }
 }
 
@@ -667,7 +690,7 @@ impl Serialize for Duration {
 
 #[cfg(feature = "std")]
 impl Serialize for net::IpAddr {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         self.to_string().serialize(serializer)
@@ -676,7 +699,7 @@ impl Serialize for net::IpAddr {
 
 #[cfg(feature = "std")]
 impl Serialize for net::Ipv4Addr {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         self.to_string().serialize(serializer)
@@ -685,7 +708,7 @@ impl Serialize for net::Ipv4Addr {
 
 #[cfg(feature = "std")]
 impl Serialize for net::Ipv6Addr {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         self.to_string().serialize(serializer)
@@ -696,7 +719,7 @@ impl Serialize for net::Ipv6Addr {
 
 #[cfg(feature = "std")]
 impl Serialize for net::SocketAddr {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         match *self {
@@ -708,7 +731,7 @@ impl Serialize for net::SocketAddr {
 
 #[cfg(feature = "std")]
 impl Serialize for net::SocketAddrV4 {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         self.to_string().serialize(serializer)
@@ -717,7 +740,7 @@ impl Serialize for net::SocketAddrV4 {
 
 #[cfg(feature = "std")]
 impl Serialize for net::SocketAddrV6 {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         self.to_string().serialize(serializer)
@@ -728,7 +751,7 @@ impl Serialize for net::SocketAddrV6 {
 
 #[cfg(feature = "std")]
 impl Serialize for path::Path {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         match self.to_str() {
@@ -740,7 +763,7 @@ impl Serialize for path::Path {
 
 #[cfg(feature = "std")]
 impl Serialize for path::PathBuf {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer,
     {
         self.as_path().serialize(serializer)
@@ -748,8 +771,12 @@ impl Serialize for path::PathBuf {
 }
 
 #[cfg(feature = "unstable")]
-impl<T> Serialize for NonZero<T> where T: Serialize + Zeroable {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error> where S: Serializer {
+impl<T> Serialize for NonZero<T>
+    where T: Serialize + Zeroable
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
         (**self).serialize(serializer)
     }
 }
diff --git a/serde/src/ser/mod.rs b/serde/src/ser/mod.rs
index 2c359b23..3b2e3d34 100644
--- a/serde/src/ser/mod.rs
+++ b/serde/src/ser/mod.rs
@@ -49,7 +49,7 @@ pub trait Error: Sized + error::Error {
 /// A trait that describes a type that can be serialized by a `Serializer`.
 pub trait Serialize {
     /// Serializes this value into this serializer.
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
         where S: Serializer;
 }
 
@@ -77,345 +77,357 @@ pub trait Serialize {
 /// state object, as it is expected that the user will not modify it. Due to the generic nature
 /// of the `Serialize` impls, modifying the object is impossible on stable Rust.
 pub trait Serializer {
-    /// The error type that can be returned if some error occurs during serialization.
+    /// Trickery to enforce correct use of the `Serialize` trait. Every
+    /// `Serializer` should set `Ok = ()`.
+    type Ok;
+
+    /// The error type when some error occurs during serialization.
     type Error: Error;
 
-    /// A state object that is initialized by `serialize_seq`, passed to
-    /// `serialize_seq_elt`, and consumed by `serialize_seq_end`. Use `()` if no
-    /// state is required.
-    type SeqState;
-    /// A state object that is initialized by `serialize_tuple`, passed to
-    /// `serialize_tuple_elt`, and consumed by `serialize_tuple_end`. Use `()`
-    /// if no state is required.
-    type TupleState;
-    /// A state object that is initialized by `serialize_tuple_struct`, passed
-    /// to `serialize_tuple_struct_elt`, and consumed by
-    /// `serialize_tuple_struct_end`. Use `()` if no state is required.
-    type TupleStructState;
-    /// A state object that is initialized by `serialize_tuple_variant`, passed
-    /// to `serialize_tuple_variant_elt`, and consumed by
-    /// `serialize_tuple_variant_end`. Use `()` if no state is required.
-    type TupleVariantState;
-    /// A state object that is initialized by `serialize_map`, passed to
-    /// `serialize_map_elt`, and consumed by `serialize_map_end`. Use `()` if no
-    /// state is required.
-    type MapState;
-    /// A state object that is initialized by `serialize_struct`, passed to
-    /// `serialize_struct_elt`, and consumed by `serialize_struct_end`. Use `()`
-    /// if no state is required.
-    type StructState;
-    /// A state object that is initialized by `serialize_struct_variant`, passed
-    /// to `serialize_struct_variant_elt`, and consumed by
-    /// `serialize_struct_variant_end`. Use `()` if no state is required.
-    type StructVariantState;
+    /// Type returned from `serialize_seq` and `serialize_seq_fixed_size` for
+    /// serializing the content of the sequence.
+    type SerializeSeq: SerializeSeq<Ok=Self::Ok, Error=Self::Error>;
+
+    /// Type returned from `serialize_tuple` for serializing the content of the
+    /// tuple.
+    type SerializeTuple: SerializeTuple<Ok=Self::Ok, Error=Self::Error>;
+
+    /// Type returned from `serialize_tuple_struct` for serializing the content
+    /// of the tuple struct.
+    type SerializeTupleStruct: SerializeTupleStruct<Ok=Self::Ok, Error=Self::Error>;
+
+    /// Type returned from `serialize_tuple_variant` for serializing the content
+    /// of the tuple variant.
+    type SerializeTupleVariant: SerializeTupleVariant<Ok=Self::Ok, Error=Self::Error>;
+
+    /// Type returned from `serialize_map` for serializing the content of the
+    /// map.
+    type SerializeMap: SerializeMap<Ok=Self::Ok, Error=Self::Error>;
+
+    /// Type returned from `serialize_struct` for serializing the content of the
+    /// struct.
+    type SerializeStruct: SerializeStruct<Ok=Self::Ok, Error=Self::Error>;
+
+    /// Type returned from `serialize_struct_variant` for serializing the
+    /// content of the struct variant.
+    type SerializeStructVariant: SerializeStructVariant<Ok=Self::Ok, Error=Self::Error>;
 
     /// Serializes a `bool` value.
-    fn serialize_bool(&mut self, v: bool) -> Result<(), Self::Error>;
+    fn serialize_bool(self, v: bool) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes an `isize` value. If the format does not differentiate
     /// between `isize` and `i64`, a reasonable implementation would be to cast
     /// the value to `i64` and forward to `serialize_i64`.
-    fn serialize_isize(&mut self, v: isize) -> Result<(), Self::Error>;
+    fn serialize_isize(self, v: isize) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes an `i8` value. If the format does not differentiate between
     /// `i8` and `i64`, a reasonable implementation would be to cast the value
     /// to `i64` and forward to `serialize_i64`.
-    fn serialize_i8(&mut self, v: i8) -> Result<(), Self::Error>;
+    fn serialize_i8(self, v: i8) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes an `i16` value. If the format does not differentiate between
     /// `i16` and `i64`, a reasonable implementation would be to cast the value
     /// to `i64` and forward to `serialize_i64`.
-    fn serialize_i16(&mut self, v: i16) -> Result<(), Self::Error>;
+    fn serialize_i16(self, v: i16) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes an `i32` value. If the format does not differentiate between
     /// `i32` and `i64`, a reasonable implementation would be to cast the value
     /// to `i64` and forward to `serialize_i64`.
-    fn serialize_i32(&mut self, v: i32) -> Result<(), Self::Error>;
+    fn serialize_i32(self, v: i32) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes an `i64` value.
-    fn serialize_i64(&mut self, v: i64) -> Result<(), Self::Error>;
+    fn serialize_i64(self, v: i64) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a `usize` value. If the format does not differentiate between
     /// `usize` and `u64`, a reasonable implementation would be to cast the
     /// value to `u64` and forward to `serialize_u64`.
-    fn serialize_usize(&mut self, v: usize) -> Result<(), Self::Error>;
+    fn serialize_usize(self, v: usize) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a `u8` value. If the format does not differentiate between
     /// `u8` and `u64`, a reasonable implementation would be to cast the value
     /// to `u64` and forward to `serialize_u64`.
-    fn serialize_u8(&mut self, v: u8) -> Result<(), Self::Error>;
+    fn serialize_u8(self, v: u8) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a `u16` value. If the format does not differentiate between
     /// `u16` and `u64`, a reasonable implementation would be to cast the value
     /// to `u64` and forward to `serialize_u64`.
-    fn serialize_u16(&mut self, v: u16) -> Result<(), Self::Error>;
+    fn serialize_u16(self, v: u16) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a `u32` value. If the format does not differentiate between
     /// `u32` and `u64`, a reasonable implementation would be to cast the value
     /// to `u64` and forward to `serialize_u64`.
-    fn serialize_u32(&mut self, v: u32) -> Result<(), Self::Error>;
+    fn serialize_u32(self, v: u32) -> Result<Self::Ok, Self::Error>;
 
     /// `Serializes a `u64` value.
-    fn serialize_u64(&mut self, v: u64) -> Result<(), Self::Error>;
+    fn serialize_u64(self, v: u64) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes an `f32` value. If the format does not differentiate between
     /// `f32` and `f64`, a reasonable implementation would be to cast the value
     /// to `f64` and forward to `serialize_f64`.
-    fn serialize_f32(&mut self, v: f32) -> Result<(), Self::Error>;
+    fn serialize_f32(self, v: f32) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes an `f64` value.
-    fn serialize_f64(&mut self, v: f64) -> Result<(), Self::Error>;
+    fn serialize_f64(self, v: f64) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a character. If the format does not support characters,
     /// it is reasonable to serialize it as a single element `str` or a `u32`.
-    fn serialize_char(&mut self, v: char) -> Result<(), Self::Error>;
+    fn serialize_char(self, v: char) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a `&str`.
-    fn serialize_str(&mut self, value: &str) -> Result<(), Self::Error>;
+    fn serialize_str(self, value: &str) -> Result<Self::Ok, Self::Error>;
 
     /// Enables serializers to serialize byte slices more compactly or more
     /// efficiently than other types of slices. If no efficient implementation
     /// is available, a reasonable implementation would be to forward to
     /// `serialize_seq`. If forwarded, the implementation looks usually just like this:
     /// ```rust
-    /// let mut state = try!(self.serialize_seq(value));
+    /// let mut seq = self.serialize_seq(Some(value.len()))?;
     /// for b in value {
-    ///     try!(self.serialize_seq_elt(&mut state, b));
+    ///     seq.serialize_element(b)?;
     /// }
-    /// self.serialize_seq_end(state)
+    /// seq.end()
     /// ```
-    fn serialize_bytes(&mut self, value: &[u8]) -> Result<(), Self::Error>;
+    fn serialize_bytes(self, value: &[u8]) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a `()` value. It's reasonable to just not serialize anything.
-    fn serialize_unit(&mut self) -> Result<(), Self::Error>;
+    fn serialize_unit(self) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a unit struct value. A reasonable implementation would be to
     /// forward to `serialize_unit`.
     fn serialize_unit_struct(
-        &mut self,
+        self,
         name: &'static str,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a unit variant, otherwise known as a variant with no
     /// arguments. A reasonable implementation would be to forward to
     /// `serialize_unit`.
     fn serialize_unit_variant(
-        &mut self,
+        self,
         name: &'static str,
         variant_index: usize,
         variant: &'static str,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::Ok, Self::Error>;
 
     /// Allows a tuple struct with a single element, also known as a newtype
     /// struct, to be more efficiently serialized than a tuple struct with
     /// multiple items. A reasonable implementation would be to forward to
     /// `serialize_tuple_struct` or to just serialize the inner value without wrapping.
     fn serialize_newtype_struct<T: Serialize>(
-        &mut self,
+        self,
         name: &'static str,
         value: T,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::Ok, Self::Error>;
 
     /// Allows a variant with a single item to be more efficiently serialized
     /// than a variant with multiple items. A reasonable implementation would be
     /// to forward to `serialize_tuple_variant`.
     fn serialize_newtype_variant<T: Serialize>(
-        &mut self,
+        self,
         name: &'static str,
         variant_index: usize,
         variant: &'static str,
         value: T,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a `None` value.
-    fn serialize_none(&mut self) -> Result<(), Self::Error>;
+    fn serialize_none(self) -> Result<Self::Ok, Self::Error>;
 
     /// Serializes a `Some(...)` value.
     fn serialize_some<T: Serialize>(
-        &mut self,
+        self,
         value: T,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::Ok, Self::Error>;
 
     /// Begins to serialize a sequence. This call must be followed by zero or
     /// more calls to `serialize_seq_elt`, then a call to `serialize_seq_end`.
     fn serialize_seq(
-        &mut self,
+        self,
         len: Option<usize>,
-    ) -> Result<Self::SeqState, Self::Error>;
-
-    /// Serializes a sequence element. Must have previously called
-    /// `serialize_seq`.
-    fn serialize_seq_elt<T: Serialize>(
-        &mut self,
-        state: &mut Self::SeqState,
-        value: T,
-    ) -> Result<(), Self::Error>;
-
-    /// Finishes serializing a sequence.
-    fn serialize_seq_end(
-        &mut self,
-        state: Self::SeqState,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::SerializeSeq, Self::Error>;
 
     /// Begins to serialize a sequence whose length will be known at
     /// deserialization time. This call must be followed by zero or more calls
     /// to `serialize_seq_elt`, then a call to `serialize_seq_end`. A reasonable
     /// implementation would be to forward to `serialize_seq`.
     fn serialize_seq_fixed_size(
-        &mut self,
+        self,
         size: usize,
-    ) -> Result<Self::SeqState, Self::Error>;
+    ) -> Result<Self::SerializeSeq, Self::Error>;
 
     /// Begins to serialize a tuple. This call must be followed by zero or more
     /// calls to `serialize_tuple_elt`, then a call to `serialize_tuple_end`. A
     /// reasonable implementation would be to forward to `serialize_seq`.
     fn serialize_tuple(
-        &mut self,
+        self,
         len: usize,
-    ) -> Result<Self::TupleState, Self::Error>;
-
-    /// Serializes a tuple element. Must have previously called
-    /// `serialize_tuple`.
-    fn serialize_tuple_elt<T: Serialize>(
-        &mut self,
-        state: &mut Self::TupleState,
-        value: T,
-    ) -> Result<(), Self::Error>;
-
-    /// Finishes serializing a tuple.
-    fn serialize_tuple_end(
-        &mut self,
-        state: Self::TupleState,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::SerializeTuple, Self::Error>;
 
     /// Begins to serialize a tuple struct. This call must be followed by zero
     /// or more calls to `serialize_tuple_struct_elt`, then a call to
     /// `serialize_tuple_struct_end`. A reasonable implementation would be to
     /// forward to `serialize_tuple`.
     fn serialize_tuple_struct(
-        &mut self,
+        self,
         name: &'static str,
         len: usize,
-    ) -> Result<Self::TupleStructState, Self::Error>;
-
-    /// Serializes a tuple struct element. Must have previously called
-    /// `serialize_tuple_struct`.
-    fn serialize_tuple_struct_elt<T: Serialize>(
-        &mut self,
-        state: &mut Self::TupleStructState,
-        value: T,
-    ) -> Result<(), Self::Error>;
-
-    /// Finishes serializing a tuple struct.
-    fn serialize_tuple_struct_end(
-        &mut self,
-        state: Self::TupleStructState,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::SerializeTupleStruct, Self::Error>;
 
     /// Begins to serialize a tuple variant. This call must be followed by zero
     /// or more calls to `serialize_tuple_variant_elt`, then a call to
     /// `serialize_tuple_variant_end`. A reasonable implementation would be to
     /// forward to `serialize_tuple_struct`.
     fn serialize_tuple_variant(
-        &mut self,
+        self,
         name: &'static str,
         variant_index: usize,
         variant: &'static str,
         len: usize,
-    ) -> Result<Self::TupleVariantState, Self::Error>;
-
-    /// Serializes a tuple variant element. Must have previously called
-    /// `serialize_tuple_variant`.
-    fn serialize_tuple_variant_elt<T: Serialize>(
-        &mut self,
-        state: &mut Self::TupleVariantState,
-        value: T,
-    ) -> Result<(), Self::Error>;
-
-    /// Finishes serializing a tuple variant.
-    fn serialize_tuple_variant_end(
-        &mut self,
-        state: Self::TupleVariantState,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::SerializeTupleVariant, Self::Error>;
 
     /// Begins to serialize a map. This call must be followed by zero or more
     /// calls to `serialize_map_key` and `serialize_map_value`, then a call to
     /// `serialize_map_end`.
     fn serialize_map(
-        &mut self,
+        self,
         len: Option<usize>,
-    ) -> Result<Self::MapState, Self::Error>;
-
-    /// Serialize a map key. Must have previously called `serialize_map`.
-    fn serialize_map_key<T: Serialize>(
-        &mut self,
-        state: &mut Self::MapState,
-        key: T
-    ) -> Result<(), Self::Error>;
-
-    /// Serialize a map value. Must have previously called `serialize_map`.
-    fn serialize_map_value<T: Serialize>(
-        &mut self,
-        state: &mut Self::MapState,
-        value: T
-    ) -> Result<(), Self::Error>;
-
-    /// Finishes serializing a map.
-    fn serialize_map_end(
-        &mut self,
-        state: Self::MapState,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::SerializeMap, Self::Error>;
 
     /// Begins to serialize a struct. This call must be followed by zero or more
     /// calls to `serialize_struct_elt`, then a call to `serialize_struct_end`.
     fn serialize_struct(
-        &mut self,
+        self,
         name: &'static str,
         len: usize,
-    ) -> Result<Self::StructState, Self::Error>;
-
-    /// Serializes a struct field. Must have previously called
-    /// `serialize_struct`.
-    fn serialize_struct_elt<V: Serialize>(
-        &mut self,
-        state: &mut Self::StructState,
-        key: &'static str,
-        value: V,
-    ) -> Result<(), Self::Error>;
-
-    /// Finishes serializing a struct.
-    fn serialize_struct_end(
-        &mut self,
-        state: Self::StructState,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::SerializeStruct, Self::Error>;
 
     /// Begins to serialize a struct variant. This call must be followed by zero
     /// or more calls to `serialize_struct_variant_elt`, then a call to
     /// `serialize_struct_variant_end`.
     fn serialize_struct_variant(
-        &mut self,
+        self,
         name: &'static str,
         variant_index: usize,
         variant: &'static str,
         len: usize,
-    ) -> Result<Self::StructVariantState, Self::Error>;
-
-    /// Serialize a struct variant element. Must have previously called
-    /// `serialize_struct_variant`.
-    fn serialize_struct_variant_elt<V: Serialize>(
-        &mut self,
-        state: &mut Self::StructVariantState,
-        key: &'static str,
-        value: V,
-    ) -> Result<(), Self::Error>;
-
-    /// Finishes serializing a struct variant.
-    fn serialize_struct_variant_end(
-        &mut self,
-        state: Self::StructVariantState,
-    ) -> Result<(), Self::Error>;
+    ) -> Result<Self::SerializeStructVariant, Self::Error>;
 }
 
+/// Returned from `Serializer::serialize_seq` and
+/// `Serializer::serialize_seq_fixed_size`.
+pub trait SerializeSeq {
+    /// Trickery to enforce correct use of the `Serialize` trait. Every
+    /// `SerializeSeq` should set `Ok = ()`.
+    type Ok;
+
+    /// The error type when some error occurs during serialization.
+    type Error: Error;
+
+    /// Serializes a sequence element.
+    fn serialize_element<T: Serialize>(&mut self, value: T) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a sequence.
+    fn end(self) -> Result<Self::Ok, Self::Error>;
+}
+
+/// Returned from `Serializer::serialize_tuple`.
+pub trait SerializeTuple {
+    /// Trickery to enforce correct use of the `Serialize` trait. Every
+    /// `SerializeTuple` should set `Ok = ()`.
+    type Ok;
+
+    /// The error type when some error occurs during serialization.
+    type Error: Error;
+
+    /// Serializes a tuple element.
+    fn serialize_element<T: Serialize>(&mut self, value: T) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a tuple.
+    fn end(self) -> Result<Self::Ok, Self::Error>;
+}
+
+/// Returned from `Serializer::serialize_tuple_struct`.
+pub trait SerializeTupleStruct {
+    /// Trickery to enforce correct use of the `Serialize` trait. Every
+    /// `SerializeTupleStruct` should set `Ok = ()`.
+    type Ok;
+
+    /// The error type when some error occurs during serialization.
+    type Error: Error;
+
+    /// Serializes a tuple struct element.
+    fn serialize_field<T: Serialize>(&mut self, value: T) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a tuple struct.
+    fn end(self) -> Result<Self::Ok, Self::Error>;
+}
+
+/// Returned from `Serializer::serialize_tuple_variant`.
+pub trait SerializeTupleVariant {
+    /// Trickery to enforce correct use of the `Serialize` trait. Every
+    /// `SerializeTupleVariant` should set `Ok = ()`.
+    type Ok;
+
+    /// The error type when some error occurs during serialization.
+    type Error: Error;
+
+    /// Serializes a tuple variant element.
+    fn serialize_field<T: Serialize>(&mut self, value: T) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a tuple variant.
+    fn end(self) -> Result<Self::Ok, Self::Error>;
+}
+
+/// Returned from `Serializer::serialize_map`.
+pub trait SerializeMap {
+    /// Trickery to enforce correct use of the `Serialize` trait. Every
+    /// `SerializeMap` should set `Ok = ()`.
+    type Ok;
+
+    /// The error type when some error occurs during serialization.
+    type Error: Error;
+
+    /// Serialize a map key.
+    fn serialize_key<T: Serialize>(&mut self, key: T) -> Result<(), Self::Error>;
+
+    /// Serialize a map value.
+    fn serialize_value<T: Serialize>(&mut self, value: T) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a map.
+    fn end(self) -> Result<Self::Ok, Self::Error>;
+}
+
+/// Returned from `Serializer::serialize_struct`.
+pub trait SerializeStruct {
+    /// Trickery to enforce correct use of the `Serialize` trait. Every
+    /// `SerializeStruct` should set `Ok = ()`.
+    type Ok;
+
+    /// The error type when some error occurs during serialization.
+    type Error: Error;
+
+    /// Serializes a struct field.
+    fn serialize_field<V: Serialize>(&mut self, key: &'static str, value: V) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a struct.
+    fn end(self) -> Result<Self::Ok, Self::Error>;
+}
+
+/// Returned from `Serializer::serialize_struct_variant`.
+pub trait SerializeStructVariant {
+    /// Trickery to enforce correct use of the `Serialize` trait. Every
+    /// `SerializeStructVariant` should set `Ok = ()`.
+    type Ok;
+
+    /// The error type when some error occurs during serialization.
+    type Error: Error;
+
+    /// Serialize a struct variant element.
+    fn serialize_field<V: Serialize>(&mut self, key: &'static str, value: V) -> Result<(), Self::Error>;
+
+    /// Finishes serializing a struct variant.
+    fn end(self) -> Result<Self::Ok, Self::Error>;
+}
 
 /// A wrapper type for iterators that implements `Serialize` for iterators whose items implement
 /// `Serialize`. Don't use multiple times. Create new versions of this with the `iterator` function
diff --git a/serde_codegen/src/ser.rs b/serde_codegen/src/ser.rs
index 01f0eb32..acd9973c 100644
--- a/serde_codegen/src/ser.rs
+++ b/serde_codegen/src/ser.rs
@@ -30,7 +30,7 @@ pub fn expand_derive_serialize(item: &syn::MacroInput) -> Result<Tokens, String>
             extern crate serde as _serde;
             #[automatically_derived]
             impl #impl_generics _serde::Serialize for #ty #where_clause {
-                fn serialize<__S>(&self, _serializer: &mut __S) -> ::std::result::Result<(), __S::Error>
+                fn serialize<__S>(&self, _serializer: __S) -> ::std::result::Result<__S::Ok, __S::Error>
                     where __S: _serde::Serializer
                 {
                     #body
@@ -159,7 +159,7 @@ fn serialize_tuple_struct(
         fields,
         impl_generics,
         false,
-        Ident::new("serialize_tuple_struct_elt"),
+        quote!(_serde::ser::SerializeTupleStruct::serialize_field),
     );
 
     let type_name = item_attrs.name().serialize_name();
@@ -169,7 +169,7 @@ fn serialize_tuple_struct(
     quote! {
         let #let_mut __serde_state = try!(_serializer.serialize_tuple_struct(#type_name, #len));
         #(#serialize_stmts)*
-        _serializer.serialize_tuple_struct_end(__serde_state)
+        _serde::ser::SerializeTupleStruct::end(__serde_state)
     }
 }
 
@@ -184,7 +184,7 @@ fn serialize_struct(
         fields,
         impl_generics,
         false,
-        Ident::new("serialize_struct_elt"),
+        quote!(_serde::ser::SerializeStruct::serialize_field),
     );
 
     let type_name = item_attrs.name().serialize_name();
@@ -210,7 +210,7 @@ fn serialize_struct(
     quote! {
         let #let_mut __serde_state = try!(_serializer.serialize_struct(#type_name, #len));
         #(#serialize_fields)*
-        _serializer.serialize_struct_end(__serde_state)
+        _serde::ser::SerializeStruct::end(__serde_state)
     }
 }
 
@@ -373,7 +373,7 @@ fn serialize_tuple_variant(
         fields,
         generics,
         true,
-        Ident::new("serialize_tuple_variant_elt"),
+        quote!(_serde::ser::SerializeTupleVariant::serialize_field),
     );
 
     let len = serialize_stmts.len();
@@ -386,7 +386,7 @@ fn serialize_tuple_variant(
             #variant_name,
             #len));
         #(#serialize_stmts)*
-        _serializer.serialize_tuple_variant_end(__serde_state)
+        _serde::ser::SerializeTupleVariant::end(__serde_state)
     }
 }
 
@@ -403,7 +403,7 @@ fn serialize_struct_variant(
         fields,
         generics,
         true,
-        Ident::new("serialize_struct_variant_elt"),
+        quote!(_serde::ser::SerializeStructVariant::serialize_field),
     );
 
     let item_name = item_attrs.name().serialize_name();
@@ -433,7 +433,7 @@ fn serialize_struct_variant(
             #len,
         ));
         #(#serialize_fields)*
-        _serializer.serialize_struct_variant_end(__serde_state)
+        _serde::ser::SerializeStructVariant::end(__serde_state)
     }
 }
 
@@ -442,7 +442,7 @@ fn serialize_tuple_struct_visitor(
     fields: &[Field],
     generics: &syn::Generics,
     is_enum: bool,
-    func: syn::Ident,
+    func: Tokens,
 ) -> Vec<Tokens> {
     fields.iter()
         .enumerate()
@@ -464,7 +464,7 @@ fn serialize_tuple_struct_visitor(
             }
 
             let ser = quote! {
-                try!(_serializer.#func(&mut __serde_state, #field_expr));
+                try!(#func(&mut __serde_state, #field_expr));
             };
 
             match skip {
@@ -480,7 +480,7 @@ fn serialize_struct_visitor(
     fields: &[Field],
     generics: &syn::Generics,
     is_enum: bool,
-    func: syn::Ident,
+    func: Tokens,
 ) -> Vec<Tokens> {
     fields.iter()
         .filter(|&field| !field.attrs.skip_serializing())
@@ -503,7 +503,7 @@ fn serialize_struct_visitor(
             }
 
             let ser = quote! {
-                try!(_serializer.#func(&mut __serde_state, #key_expr, #field_expr));
+                try!(#func(&mut __serde_state, #key_expr, #field_expr));
             };
 
             match skip {
@@ -541,7 +541,7 @@ fn wrap_serialize_with(
         }
 
         impl #wrapper_generics _serde::Serialize for #wrapper_ty #where_clause {
-            fn serialize<__S>(&self, __s: &mut __S) -> ::std::result::Result<(), __S::Error>
+            fn serialize<__S>(&self, __s: __S) -> ::std::result::Result<__S::Ok, __S::Error>
                 where __S: _serde::Serializer
             {
                 #path(self.value, __s)
@@ -558,7 +558,7 @@ fn wrap_serialize_with(
 // Serialization of an empty struct results in code like:
 //
 //     let mut __serde_state = try!(serializer.serialize_struct("S", 0));
-//     serializer.serialize_struct_end(__serde_state)
+//     _serde::ser::SerializeStruct::end(__serde_state)
 //
 // where we want to omit the `mut` to avoid a warning.
 fn mut_if(is_mut: bool) -> Option<Tokens> {
diff --git a/serde_test/src/ser.rs b/serde_test/src/ser.rs
index 82c31847..60c50125 100644
--- a/serde_test/src/ser.rs
+++ b/serde_test/src/ser.rs
@@ -1,9 +1,6 @@
 use std::marker::PhantomData;
 
-use serde::ser::{
-    self,
-    Serialize,
-};
+use serde::{ser, Serialize};
 
 use error::Error;
 use token::Token;
@@ -30,178 +27,119 @@ impl<'a, I> Serializer<'a, I>
     }
 }
 
-impl<'a, I> ser::Serializer for Serializer<'a, I>
+impl<'s, 'a, I> ser::Serializer for &'s mut Serializer<'a, I>
     where I: Iterator<Item=&'a Token<'a>>,
 {
+    type Ok = ();
     type Error = Error;
-    type MapState = ();
-    type SeqState = ();
-    type TupleState = ();
-    type TupleStructState = ();
-    type TupleVariantState = ();
-    type StructState = ();
-    type StructVariantState = ();
 
-    fn serialize_unit(&mut self) -> Result<(), Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::Unit));
-        Ok(())
-    }
+    type SerializeSeq = Self;
+    type SerializeTuple = Self;
+    type SerializeTupleStruct = Self;
+    type SerializeTupleVariant = Self;
+    type SerializeMap = Self;
+    type SerializeStruct = Self;
+    type SerializeStructVariant = Self;
 
-    fn serialize_newtype_variant<T>(&mut self,
-                                name: &str,
-                                _variant_index: usize,
-                                variant: &str,
-                                value: T) -> Result<(), Error>
-        where T: Serialize,
-    {
-        assert_eq!(self.tokens.next(), Some(&Token::EnumNewType(name, variant)));
-        value.serialize(self)
-    }
-
-    fn serialize_unit_struct(&mut self, name: &str) -> Result<(), Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::UnitStruct(name)));
-        Ok(())
-    }
-
-    fn serialize_unit_variant(&mut self,
-                          name: &str,
-                          _variant_index: usize,
-                          variant: &str) -> Result<(), Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::EnumUnit(name, variant)));
-
-        Ok(())
-    }
-
-    fn serialize_bool(&mut self, v: bool) -> Result<(), Error> {
+    fn serialize_bool(self, v: bool) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::Bool(v)));
         Ok(())
     }
 
-    fn serialize_isize(&mut self, v: isize) -> Result<(), Error> {
+    fn serialize_isize(self, v: isize) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::Isize(v)));
         Ok(())
     }
 
-    fn serialize_i8(&mut self, v: i8) -> Result<(), Error> {
+    fn serialize_i8(self, v: i8) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::I8(v)));
         Ok(())
     }
 
-    fn serialize_i16(&mut self, v: i16) -> Result<(), Error> {
+    fn serialize_i16(self, v: i16) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::I16(v)));
         Ok(())
     }
 
-    fn serialize_i32(&mut self, v: i32) -> Result<(), Error> {
+    fn serialize_i32(self, v: i32) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::I32(v)));
         Ok(())
     }
 
-    fn serialize_i64(&mut self, v: i64) -> Result<(), Error> {
+    fn serialize_i64(self, v: i64) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::I64(v)));
         Ok(())
     }
 
-    fn serialize_usize(&mut self, v: usize) -> Result<(), Error> {
+    fn serialize_usize(self, v: usize) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::Usize(v)));
         Ok(())
     }
 
-    fn serialize_u8(&mut self, v: u8) -> Result<(), Error> {
+    fn serialize_u8(self, v: u8) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::U8(v)));
         Ok(())
     }
 
-    fn serialize_u16(&mut self, v: u16) -> Result<(), Error> {
+    fn serialize_u16(self, v: u16) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::U16(v)));
         Ok(())
     }
 
-    fn serialize_u32(&mut self, v: u32) -> Result<(), Error> {
+    fn serialize_u32(self, v: u32) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::U32(v)));
         Ok(())
     }
 
-    fn serialize_u64(&mut self, v: u64) -> Result<(), Error> {
+    fn serialize_u64(self, v: u64) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::U64(v)));
         Ok(())
     }
 
-    fn serialize_f32(&mut self, v: f32) -> Result<(), Error> {
+    fn serialize_f32(self, v: f32) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::F32(v)));
         Ok(())
     }
 
-    fn serialize_f64(&mut self, v: f64) -> Result<(), Error> {
+    fn serialize_f64(self, v: f64) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::F64(v)));
         Ok(())
     }
 
-    fn serialize_char(&mut self, v: char) -> Result<(), Error> {
+    fn serialize_char(self, v: char) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::Char(v)));
         Ok(())
     }
 
-    fn serialize_str(&mut self, v: &str) -> Result<(), Error> {
+    fn serialize_str(self, v: &str) -> Result<(), Error> {
         assert_eq!(self.tokens.next(), Some(&Token::Str(v)));
         Ok(())
     }
 
-    fn serialize_none(&mut self) -> Result<(), Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::Option(false)));
+    fn serialize_bytes(self, value: &[u8]) -> Result<(), Self::Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::Bytes(value)));
         Ok(())
     }
 
-    fn serialize_some<V>(&mut self, value: V) -> Result<(), Error>
-        where V: Serialize,
-    {
-        assert_eq!(self.tokens.next(), Some(&Token::Option(true)));
-        value.serialize(self)
-    }
-
-    fn serialize_seq<'b>(&'b mut self, len: Option<usize>) -> Result<(), Error>
-    {
-        assert_eq!(self.tokens.next(), Some(&Token::SeqStart(len)));
+    fn serialize_unit(self) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::Unit));
         Ok(())
     }
 
-    fn serialize_seq_elt<T>(&mut self, _: &mut (), value: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        assert_eq!(self.tokens.next(), Some(&Token::SeqSep));
-        value.serialize(self)
-    }
-
-    fn serialize_seq_end(&mut self, _: ()) -> Result<(), Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::SeqEnd));
+    fn serialize_unit_struct(self, name: &str) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::UnitStruct(name)));
         Ok(())
     }
 
-    fn serialize_seq_fixed_size(&mut self, len: usize) -> Result<(), Error>
-    {
-        assert_eq!(self.tokens.next(), Some(&Token::SeqArrayStart(len)));
+    fn serialize_unit_variant(self,
+                              name: &str,
+                              _variant_index: usize,
+                              variant: &str) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::EnumUnit(name, variant)));
         Ok(())
     }
 
-    fn serialize_tuple(&mut self, len: usize) -> Result<(), Error>
-    {
-        assert_eq!(self.tokens.next(), Some(&Token::TupleStart(len)));
-        Ok(())
-    }
-
-    fn serialize_tuple_elt<T>(&mut self, _: &mut (), value: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        assert_eq!(self.tokens.next(), Some(&Token::TupleSep));
-        value.serialize(self)
-    }
-
-    fn serialize_tuple_end(&mut self, _: ()) -> Result<(), Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::TupleEnd));
-        Ok(())
-    }
-
-    fn serialize_newtype_struct<T>(&mut self,
+    fn serialize_newtype_struct<T>(self,
                                    name: &'static str,
                                    value: T) -> Result<(), Error>
         where T: Serialize,
@@ -210,114 +148,209 @@ impl<'a, I> ser::Serializer for Serializer<'a, I>
         value.serialize(self)
     }
 
-    fn serialize_tuple_struct(&mut self, name: &'static str, len: usize) -> Result<(), Error>
+    fn serialize_newtype_variant<T>(self,
+                                    name: &str,
+                                    _variant_index: usize,
+                                    variant: &str,
+                                    value: T) -> Result<(), Error>
+        where T: Serialize,
     {
-        assert_eq!(self.tokens.next(), Some(&Token::TupleStructStart(name, len)));
-
-        Ok(())
-    }
-
-    fn serialize_tuple_struct_elt<T>(&mut self, _: &mut (), value: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        assert_eq!(self.tokens.next(), Some(&Token::TupleStructSep));
+        assert_eq!(self.tokens.next(), Some(&Token::EnumNewType(name, variant)));
         value.serialize(self)
     }
 
-    fn serialize_tuple_struct_end(&mut self, _: ()) -> Result<(), Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::TupleStructEnd));
+    fn serialize_none(self) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::Option(false)));
         Ok(())
     }
 
-    fn serialize_tuple_variant(&mut self,
+    fn serialize_some<V>(self, value: V) -> Result<(), Error>
+        where V: Serialize,
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::Option(true)));
+        value.serialize(self)
+    }
+
+    fn serialize_seq(self, len: Option<usize>) -> Result<Self, Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::SeqStart(len)));
+        Ok(self)
+    }
+
+    fn serialize_seq_fixed_size(self, len: usize) -> Result<Self, Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::SeqArrayStart(len)));
+        Ok(self)
+    }
+
+    fn serialize_tuple(self, len: usize) -> Result<Self, Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleStart(len)));
+        Ok(self)
+    }
+
+    fn serialize_tuple_struct(self, name: &'static str, len: usize) -> Result<Self, Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleStructStart(name, len)));
+        Ok(self)
+    }
+
+    fn serialize_tuple_variant(self,
                                name: &str,
                                _variant_index: usize,
                                variant: &str,
-                               len: usize) -> Result<(), Error>
+                               len: usize) -> Result<Self, Error>
     {
         assert_eq!(self.tokens.next(), Some(&Token::EnumSeqStart(name, variant, len)));
-
-        Ok(())
+        Ok(self)
     }
 
-    fn serialize_tuple_variant_elt<T>(&mut self, _: &mut (), value: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        assert_eq!(self.tokens.next(), Some(&Token::EnumSeqSep));
-        value.serialize(self)
-    }
-
-    fn serialize_tuple_variant_end(&mut self, _: ()) -> Result<(), Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::EnumSeqEnd));
-        Ok(())
-    }
-
-    fn serialize_map(&mut self, len: Option<usize>) -> Result<(), Error>
-    {
+    fn serialize_map(self, len: Option<usize>) -> Result<Self, Error> {
         assert_eq!(self.tokens.next(), Some(&Token::MapStart(len)));
-
-        Ok(())
+        Ok(self)
     }
 
-    fn serialize_map_key<T>(&mut self, _: &mut (), key: T) -> Result<(), Self::Error> where T: Serialize {
-        assert_eq!(self.tokens.next(), Some(&Token::MapSep));
-        key.serialize(self)
-    }
-
-    fn serialize_map_value<T>(&mut self, _: &mut (), value: T) -> Result<(), Self::Error> where T: Serialize {
-        value.serialize(self)
-    }
-
-    fn serialize_map_end(&mut self, _: ()) -> Result<(), Self::Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::MapEnd));
-        Ok(())
-    }
-
-    fn serialize_struct(&mut self, name: &str, len: usize) -> Result<(), Error>
-    {
+    fn serialize_struct(self, name: &str, len: usize) -> Result<Self, Error> {
         assert_eq!(self.tokens.next(), Some(&Token::StructStart(name, len)));
-
-        Ok(())
+        Ok(self)
     }
 
-    fn serialize_struct_elt<V>(&mut self, _: &mut (), key: &'static str, value: V) -> Result<(), Self::Error> where V: Serialize {
-        assert_eq!(self.tokens.next(), Some(&Token::StructSep));
-        try!(key.serialize(self));
-        value.serialize(self)
-    }
-
-    fn serialize_struct_end(&mut self, _: ()) -> Result<(), Self::Error> {
-        assert_eq!(self.tokens.next(), Some(&Token::StructEnd));
-        Ok(())
-    }
-
-    fn serialize_struct_variant(&mut self,
+    fn serialize_struct_variant(self,
                                 name: &str,
                                 _variant_index: usize,
                                 variant: &str,
-                                len: usize) -> Result<(), Error>
+                                len: usize) -> Result<Self, Error>
     {
         assert_eq!(self.tokens.next(), Some(&Token::EnumMapStart(name, variant, len)));
+        Ok(self)
+    }
+}
 
+impl<'s, 'a, I> ser::SerializeSeq for &'s mut Serializer<'a, I>
+    where I: Iterator<Item=&'a Token<'a>>,
+{
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_element<T>(&mut self, value: T) -> Result<(), Error>
+        where T: Serialize
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::SeqSep));
+        value.serialize(&mut **self)
+    }
+
+    fn end(self) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::SeqEnd));
         Ok(())
     }
+}
 
-    fn serialize_struct_variant_elt<V>(&mut self, _: &mut (), key: &'static str, value: V) -> Result<(), Self::Error> where V: Serialize {
-        assert_eq!(self.tokens.next(), Some(&Token::EnumMapSep));
-        try!(key.serialize(self));
-        value.serialize(self)
+impl<'s, 'a, I> ser::SerializeTuple for &'s mut Serializer<'a, I>
+    where I: Iterator<Item=&'a Token<'a>>,
+{
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_element<T>(&mut self, value: T) -> Result<(), Error>
+        where T: Serialize
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleSep));
+        value.serialize(&mut **self)
     }
 
-    fn serialize_struct_variant_end(&mut self, _: ()) -> Result<(), Self::Error> {
+    fn end(self) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleEnd));
+        Ok(())
+    }
+}
+
+impl<'s, 'a, I> ser::SerializeTupleStruct for &'s mut Serializer<'a, I>
+    where I: Iterator<Item=&'a Token<'a>>,
+{
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, value: T) -> Result<(), Error>
+        where T: Serialize
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleStructSep));
+        value.serialize(&mut **self)
+    }
+
+    fn end(self) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleStructEnd));
+        Ok(())
+    }
+}
+
+impl<'s, 'a, I> ser::SerializeTupleVariant for &'s mut Serializer<'a, I>
+    where I: Iterator<Item=&'a Token<'a>>,
+{
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<T>(&mut self, value: T) -> Result<(), Error>
+        where T: Serialize
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::EnumSeqSep));
+        value.serialize(&mut **self)
+    }
+
+    fn end(self) -> Result<(), Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::EnumSeqEnd));
+        Ok(())
+    }
+}
+
+impl<'s, 'a, I> ser::SerializeMap for &'s mut Serializer<'a, I>
+    where I: Iterator<Item=&'a Token<'a>>,
+{
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_key<T>(&mut self, key: T) -> Result<(), Self::Error> where T: Serialize {
+        assert_eq!(self.tokens.next(), Some(&Token::MapSep));
+        key.serialize(&mut **self)
+    }
+
+    fn serialize_value<T>(&mut self, value: T) -> Result<(), Self::Error> where T: Serialize {
+        value.serialize(&mut **self)
+    }
+
+    fn end(self) -> Result<(), Self::Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::MapEnd));
+        Ok(())
+    }
+}
+
+impl<'s, 'a, I> ser::SerializeStruct for &'s mut Serializer<'a, I>
+    where I: Iterator<Item=&'a Token<'a>>,
+{
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<V>(&mut self, key: &'static str, value: V) -> Result<(), Self::Error> where V: Serialize {
+        assert_eq!(self.tokens.next(), Some(&Token::StructSep));
+        try!(key.serialize(&mut **self));
+        value.serialize(&mut **self)
+    }
+
+    fn end(self) -> Result<(), Self::Error> {
+        assert_eq!(self.tokens.next(), Some(&Token::StructEnd));
+        Ok(())
+    }
+}
+
+impl<'s, 'a, I> ser::SerializeStructVariant for &'s mut Serializer<'a, I>
+    where I: Iterator<Item=&'a Token<'a>>,
+{
+    type Ok = ();
+    type Error = Error;
+
+    fn serialize_field<V>(&mut self, key: &'static str, value: V) -> Result<(), Self::Error> where V: Serialize {
+        assert_eq!(self.tokens.next(), Some(&Token::EnumMapSep));
+        try!(key.serialize(&mut **self));
+        value.serialize(&mut **self)
+    }
+
+    fn end(self) -> Result<(), Self::Error> {
         assert_eq!(self.tokens.next(), Some(&Token::EnumMapEnd));
         Ok(())
     }
-
-    fn serialize_bytes(&mut self, value: &[u8]) -> Result<(), Self::Error> {
-        let mut state = try!(self.serialize_seq(Some(value.len())));
-        for c in value {
-            try!(self.serialize_seq_elt(&mut state, c));
-        }
-        self.serialize_seq_end(state)
-    }
 }
diff --git a/testing/tests/test_annotations.rs b/testing/tests/test_annotations.rs
index b2971fea..0649a8e7 100644
--- a/testing/tests/test_annotations.rs
+++ b/testing/tests/test_annotations.rs
@@ -20,7 +20,7 @@ trait ShouldSkip: Sized {
 }
 
 trait SerializeWith: Sized {
-    fn serialize_with<S>(&self, ser: &mut S) -> Result<(), S::Error>
+    fn serialize_with<S>(&self, ser: S) -> Result<S::Ok, S::Error>
         where S: Serializer;
 }
 
@@ -38,7 +38,7 @@ impl ShouldSkip for i32 {
 }
 
 impl SerializeWith for i32 {
-    fn serialize_with<S>(&self, ser: &mut S) -> Result<(), S::Error>
+    fn serialize_with<S>(&self, ser: S) -> Result<S::Ok, S::Error>
         where S: Serializer
     {
         if *self == 123 {
@@ -642,7 +642,7 @@ struct NotSerializeStruct(i8);
 enum NotSerializeEnum { Trouble }
 
 impl SerializeWith for NotSerializeEnum {
-    fn serialize_with<S>(&self, ser: &mut S) -> Result<(), S::Error>
+    fn serialize_with<S>(&self, ser: S) -> Result<S::Ok, S::Error>
         where S: Serializer
     {
         "trouble".serialize(ser)
diff --git a/testing/tests/test_bytes.rs b/testing/tests/test_bytes.rs
index a0e5fbcc..6968f900 100644
--- a/testing/tests/test_bytes.rs
+++ b/testing/tests/test_bytes.rs
@@ -1,312 +1,20 @@
-use std::fmt;
-use std::error;
-
-use serde::{Serialize, Serializer};
 use serde::bytes::{ByteBuf, Bytes};
-use serde::ser;
-use serde::de;
-
-use serde_test::{assert_de_tokens, Token};
-
-///////////////////////////////////////////////////////////////////////////////
-
-#[derive(Debug, PartialEq)]
-struct Error;
-
-impl ser::Error for Error {
-    fn custom<T: Into<String>>(_: T) -> Error { Error }
-}
-
-impl de::Error for Error {
-    fn custom<T: Into<String>>(_: T) -> Error { Error }
-
-    fn end_of_stream() -> Error { Error }
-}
-
-impl fmt::Display for Error {
-    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
-        formatter.write_str(format!("{:?}", self).as_ref())
-    }
-}
-
-impl error::Error for Error {
-    fn description(&self) -> &str {
-        "Serde Deserialization Error"
-    }
-
-    fn cause(&self) -> Option<&error::Error> {
-        None
-    }
-}
-
-///////////////////////////////////////////////////////////////////////////////
-
-struct BytesSerializer {
-    bytes: Vec<u8>,
-}
-
-impl BytesSerializer {
-    fn new(bytes: Vec<u8>) -> Self {
-        BytesSerializer {
-            bytes: bytes,
-        }
-    }
-}
-
-impl Serializer for BytesSerializer {
-    type Error = Error;
-    type SeqState = ();
-    type MapState = ();
-    type TupleState = ();
-    type TupleStructState = ();
-    type TupleVariantState = ();
-    type StructState = ();
-    type StructVariantState = ();
-
-    fn serialize_unit(&mut self) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_unit_struct(&mut self, _name: &'static str) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_unit_variant(&mut self, _: &'static str, _: usize, _: &'static str) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_bool(&mut self, _v: bool) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_isize(&mut self, _v: isize) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_usize(&mut self, _v: usize) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_i8(&mut self, _v: i8) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_u8(&mut self, _v: u8) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_i16(&mut self, _v: i16) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_u16(&mut self, _v: u16) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_i32(&mut self, _v: i32) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_u32(&mut self, _v: u32) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_i64(&mut self, _v: i64) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_u64(&mut self, _v: u64) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_f32(&mut self, _v: f32) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_f64(&mut self, _v: f64) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_char(&mut self, _v: char) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_str(&mut self, _v: &str) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_none(&mut self) -> Result<(), Error> {
-        Err(Error)
-    }
-
-    fn serialize_some<V>(&mut self, _value: V) -> Result<(), Error>
-        where V: Serialize,
-    {
-        Err(Error)
-    }
-
-    fn serialize_newtype_struct<V>(&mut self, _: &'static str, _value: V) -> Result<(), Error>
-        where V: Serialize,
-    {
-        Err(Error)
-    }
-
-    fn serialize_newtype_variant<V>(&mut self, _: &'static str, _: usize, _: &'static str, _value: V) -> Result<(), Error>
-        where V: Serialize,
-    {
-        Err(Error)
-    }
-
-    fn serialize_seq(&mut self, _len: Option<usize>) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_seq_fixed_size(&mut self, _len: usize) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_seq_elt<T>(&mut self, _: &mut (), _value: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        Err(Error)
-    }
-
-    fn serialize_seq_end(&mut self, _: ()) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_tuple(&mut self, _len: usize) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_tuple_elt<T>(&mut self, _: &mut (), _value: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        Err(Error)
-    }
-
-    fn serialize_tuple_end(&mut self, _: ()) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_tuple_struct(&mut self, _: &'static str, _len: usize) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_tuple_struct_elt<T>(&mut self, _: &mut (), _value: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        Err(Error)
-    }
-
-    fn serialize_tuple_struct_end(&mut self, _: ()) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_tuple_variant(&mut self, _: &'static str, _: usize, _: &'static str, _len: usize) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_tuple_variant_elt<T>(&mut self, _: &mut (), _value: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        Err(Error)
-    }
-
-    fn serialize_tuple_variant_end(&mut self, _: ()) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_map(&mut self, _: Option<usize>) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_map_key<T>(&mut self, _: &mut (), _key: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        Err(Error)
-    }
-
-    fn serialize_map_value<T>(&mut self, _: &mut (), _value: T) -> Result<(), Error>
-        where T: Serialize
-    {
-        Err(Error)
-    }
-
-    fn serialize_map_end(&mut self, _: ()) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_struct(&mut self, _: &'static str, _: usize) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_struct_elt<V>(&mut self, _: &mut (), _key: &'static str, _value: V) -> Result<(), Error>
-        where V: Serialize,
-    {
-        Err(Error)
-    }
-
-    fn serialize_struct_end(&mut self, _: ()) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_struct_variant(&mut self, _: &'static str, _: usize, _: &'static str, _: usize) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_struct_variant_elt<V>(&mut self, _: &mut (), _key: &'static str, _value: V) -> Result<(), Error>
-        where V: Serialize,
-    {
-        Err(Error)
-    }
-
-    fn serialize_struct_variant_end(&mut self, _: ()) -> Result<(), Error>
-    {
-        Err(Error)
-    }
-
-    fn serialize_bytes(&mut self, bytes: &[u8]) -> Result<(), Error> {
-        assert_eq!(self.bytes, bytes);
-        Ok(())
-    }
-}
-
-///////////////////////////////////////////////////////////////////////////////
+use serde_test::{assert_tokens, assert_ser_tokens, assert_de_tokens, Token};
 
 #[test]
-fn test_bytes_ser_bytes() {
-    let buf = vec![];
-    let bytes = Bytes::from(&buf);
-    let mut ser = BytesSerializer::new(vec![]);
-    bytes.serialize(&mut ser).unwrap();
+fn test_bytes() {
+    let empty = Bytes::new(&[]);
+    assert_ser_tokens(&empty, &[Token::Bytes(b"")]);
 
-    let buf = vec![1, 2, 3];
-    let bytes = Bytes::from(&buf);
-    let mut ser = BytesSerializer::new(vec![1, 2, 3]);
-    bytes.serialize(&mut ser).unwrap();
+    let buf = vec![65, 66, 67];
+    let bytes = Bytes::new(&buf);
+    assert_ser_tokens(&bytes, &[Token::Bytes(b"ABC")]);
 }
 
-///////////////////////////////////////////////////////////////////////////////
-
 #[test]
-fn test_byte_buf_de() {
+fn test_byte_buf() {
     let empty = ByteBuf::new();
-    assert_de_tokens(&empty, &[Token::Bytes(b""),]);
+    assert_tokens(&empty, &[Token::Bytes(b"")]);
     assert_de_tokens(&empty, &[Token::Str("")]);
     assert_de_tokens(&empty, &[Token::String(String::new())]);
     assert_de_tokens(&empty, &[
@@ -319,7 +27,7 @@ fn test_byte_buf_de() {
     ]);
 
     let buf = ByteBuf::from(vec![65, 66, 67]);
-    assert_de_tokens(&buf, &[Token::Bytes(b"ABC")]);
+    assert_tokens(&buf, &[Token::Bytes(b"ABC")]);
     assert_de_tokens(&buf, &[Token::Str("ABC")]);
     assert_de_tokens(&buf, &[Token::String("ABC".to_owned())]);
     assert_de_tokens(&buf, &[
diff --git a/testing/tests/test_gen.rs b/testing/tests/test_gen.rs
index 3945a924..34b5c469 100644
--- a/testing/tests/test_gen.rs
+++ b/testing/tests/test_gen.rs
@@ -295,7 +295,7 @@ fn assert<T: Serialize + Deserialize>() {}
 fn assert_ser<T: Serialize>() {}
 
 trait SerializeWith {
-    fn serialize_with<S: Serializer>(_: &Self, _: &mut S) -> StdResult<(), S::Error>;
+    fn serialize_with<S: Serializer>(_: &Self, _: S) -> StdResult<S::Ok, S::Error>;
 }
 
 trait DeserializeWith: Sized {
@@ -305,7 +305,7 @@ trait DeserializeWith: Sized {
 // Implements neither Serialize nor Deserialize
 struct X;
 
-fn ser_x<S: Serializer>(_: &X, _: &mut S) -> StdResult<(), S::Error> {
+fn ser_x<S: Serializer>(_: &X, _: S) -> StdResult<S::Ok, S::Error> {
     unimplemented!()
 }
 
@@ -314,7 +314,7 @@ fn de_x<D: Deserializer>(_: D) -> StdResult<X, D::Error> {
 }
 
 impl SerializeWith for X {
-    fn serialize_with<S: Serializer>(_: &Self, _: &mut S) -> StdResult<(), S::Error> {
+    fn serialize_with<S: Serializer>(_: &Self, _: S) -> StdResult<S::Ok, S::Error> {
         unimplemented!()
     }
 }