diff --git a/serde_test/src/ser.rs b/serde_test/src/ser.rs
index 82c31847..85af06e0 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_elem<T>(&mut self, value: T) -> Result<(), Error>
+        where T: Serialize
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::SeqSep));
+        value.serialize(&mut **self)
+    }
+
+    fn serialize_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_elem<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 serialize_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_elem<T>(&mut self, value: T) -> Result<(), Error>
+        where T: Serialize
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::TupleStructSep));
+        value.serialize(&mut **self)
+    }
+
+    fn serialize_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_elem<T>(&mut self, value: T) -> Result<(), Error>
+        where T: Serialize
+    {
+        assert_eq!(self.tokens.next(), Some(&Token::EnumSeqSep));
+        value.serialize(&mut **self)
+    }
+
+    fn serialize_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 serialize_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 serialize_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 serialize_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)
-    }
 }