src/pkg/gob/gobencdec_test.go - go - Git at Google

 // Copyright 20011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // This file contains tests of the GobEncoder/GobDecoder support.

 package gob

 import (
 	"bytes"
 	"fmt"
 	"os"
 	"strings"
 	"testing"
 )

 // Types that implement the GobEncoder/Decoder interfaces.

 type ByteStruct struct {
 	a byte // not an exported field
 }

 type StringStruct struct {
 	s string // not an exported field
 }

 type ArrayStruct struct {
 	a [8192]byte // not an exported field
 }

 type Gobber int

 type ValueGobber string // encodes with a value, decodes with a pointer.

 // The relevant methods

 func (g *ByteStruct) GobEncode() ([]byte, os.Error) {
 	b := make([]byte, 3)
 	b[0] = g.a
 	b[1] = g.a + 1
 	b[2] = g.a + 2
 	return b, nil
 }

 func (g *ByteStruct) GobDecode(data []byte) os.Error {
 	if g == nil {
 		return os.NewError("NIL RECEIVER")
 	}
 	// Expect N sequential-valued bytes.
 	if len(data) == 0 {
 		return os.EOF
 	}
 	g.a = data[0]
 	for i, c := range data {
 		if c != g.a+byte(i) {
 			return os.NewError("invalid data sequence")
 		}
 	}
 	return nil
 }

 func (g *StringStruct) GobEncode() ([]byte, os.Error) {
 	return []byte(g.s), nil
 }

 func (g *StringStruct) GobDecode(data []byte) os.Error {
 	// Expect N sequential-valued bytes.
 	if len(data) == 0 {
 		return os.EOF
 	}
 	a := data[0]
 	for i, c := range data {
 		if c != a+byte(i) {
 			return os.NewError("invalid data sequence")
 		}
 	}
 	g.s = string(data)
 	return nil
 }

 func (a *ArrayStruct) GobEncode() ([]byte, os.Error) {
 	return a.a[:], nil
 }

 func (a *ArrayStruct) GobDecode(data []byte) os.Error {
 	if len(data) != len(a.a) {
 		return os.NewError("wrong length in array decode")
 	}
 	copy(a.a[:], data)
 	return nil
 }

 func (g *Gobber) GobEncode() ([]byte, os.Error) {
 	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
 }

 func (g *Gobber) GobDecode(data []byte) os.Error {
 	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
 	return err
 }

 func (v ValueGobber) GobEncode() ([]byte, os.Error) {
 	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
 }

 func (v *ValueGobber) GobDecode(data []byte) os.Error {
 	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
 	return err
 }

 // Structs that include GobEncodable fields.

 type GobTest0 struct {
 	X int // guarantee we have  something in common with GobTest*
 	G *ByteStruct
 }

 type GobTest1 struct {
 	X int // guarantee we have  something in common with GobTest*
 	G *StringStruct
 }

 type GobTest2 struct {
 	X int    // guarantee we have  something in common with GobTest*
 	G string // not a GobEncoder - should give us errors
 }

 type GobTest3 struct {
 	X int // guarantee we have  something in common with GobTest*
 	G *Gobber
 }

 type GobTest4 struct {
 	X int // guarantee we have  something in common with GobTest*
 	V ValueGobber
 }

 type GobTest5 struct {
 	X int // guarantee we have  something in common with GobTest*
 	V *ValueGobber
 }

 type GobTestIgnoreEncoder struct {
 	X int // guarantee we have  something in common with GobTest*
 }

 type GobTestValueEncDec struct {
 	X int          // guarantee we have  something in common with GobTest*
 	G StringStruct // not a pointer.
 }

 type GobTestIndirectEncDec struct {
 	X int             // guarantee we have  something in common with GobTest*
 	G ***StringStruct // indirections to the receiver.
 }

 type GobTestArrayEncDec struct {
 	X int         // guarantee we have  something in common with GobTest*
 	A ArrayStruct // not a pointer.
 }

 type GobTestIndirectArrayEncDec struct {
 	X int            // guarantee we have  something in common with GobTest*
 	A ***ArrayStruct // indirections to a large receiver.
 }

 func TestGobEncoderField(t *testing.T) {
 	b := new(bytes.Buffer)
 	// First a field that's a structure.
 	enc := NewEncoder(b)
 	err := enc.Encode(GobTest0{17, &ByteStruct{'A'}})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(GobTest0)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if x.G.a != 'A' {
 		t.Errorf("expected 'A' got %c", x.G.a)
 	}
 	// Now a field that's not a structure.
 	b.Reset()
 	gobber := Gobber(23)
 	err = enc.Encode(GobTest3{17, &gobber})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	y := new(GobTest3)
 	err = dec.Decode(y)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if *y.G != 23 {
 		t.Errorf("expected '23 got %d", *y.G)
 	}
 }

 // Even though the field is a value, we can still take its address
 // and should be able to call the methods.
 func TestGobEncoderValueField(t *testing.T) {
 	b := new(bytes.Buffer)
 	// First a field that's a structure.
 	enc := NewEncoder(b)
 	err := enc.Encode(GobTestValueEncDec{17, StringStruct{"HIJKL"}})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(GobTestValueEncDec)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if x.G.s != "HIJKL" {
 		t.Errorf("expected `HIJKL` got %s", x.G.s)
 	}
 }

 // GobEncode/Decode should work even if the value is
 // more indirect than the receiver.
 func TestGobEncoderIndirectField(t *testing.T) {
 	b := new(bytes.Buffer)
 	// First a field that's a structure.
 	enc := NewEncoder(b)
 	s := &StringStruct{"HIJKL"}
 	sp := &s
 	err := enc.Encode(GobTestIndirectEncDec{17, &sp})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(GobTestIndirectEncDec)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if (***x.G).s != "HIJKL" {
 		t.Errorf("expected `HIJKL` got %s", (***x.G).s)
 	}
 }

 // Test with a large field with methods.
 func TestGobEncoderArrayField(t *testing.T) {
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
 	var a GobTestArrayEncDec
 	a.X = 17
 	for i := range a.A.a {
 		a.A.a[i] = byte(i)
 	}
 	err := enc.Encode(a)
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(GobTestArrayEncDec)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	for i, v := range x.A.a {
 		if v != byte(i) {
 			t.Errorf("expected %x got %x", byte(i), v)
 			break
 		}
 	}
 }

 // Test an indirection to a large field with methods.
 func TestGobEncoderIndirectArrayField(t *testing.T) {
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
 	var a GobTestIndirectArrayEncDec
 	a.X = 17
 	var array ArrayStruct
 	ap := &array
 	app := &ap
 	a.A = &app
 	for i := range array.a {
 		array.a[i] = byte(i)
 	}
 	err := enc.Encode(a)
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(GobTestIndirectArrayEncDec)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	for i, v := range (***x.A).a {
 		if v != byte(i) {
 			t.Errorf("expected %x got %x", byte(i), v)
 			break
 		}
 	}
 }

 // As long as the fields have the same name and implement the
 // interface, we can cross-connect them.  Not sure it's useful
 // and may even be bad but it works and it's hard to prevent
 // without exposing the contents of the object, which would
 // defeat the purpose.
 func TestGobEncoderFieldsOfDifferentType(t *testing.T) {
 	// first, string in field to byte in field
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
 	err := enc.Encode(GobTest1{17, &StringStruct{"ABC"}})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(GobTest0)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if x.G.a != 'A' {
 		t.Errorf("expected 'A' got %c", x.G.a)
 	}
 	// now the other direction, byte in field to string in field
 	b.Reset()
 	err = enc.Encode(GobTest0{17, &ByteStruct{'X'}})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	y := new(GobTest1)
 	err = dec.Decode(y)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if y.G.s != "XYZ" {
 		t.Fatalf("expected `XYZ` got %c", y.G.s)
 	}
 }

 // Test that we can encode a value and decode into a pointer.
 func TestGobEncoderValueEncoder(t *testing.T) {
 	// first, string in field to byte in field
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
 	err := enc.Encode(GobTest4{17, ValueGobber("hello")})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(GobTest5)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if *x.V != "hello" {
 		t.Errorf("expected `hello` got %s", x.V)
 	}
 }

 func TestGobEncoderFieldTypeError(t *testing.T) {
 	// GobEncoder to non-decoder: error
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
 	err := enc.Encode(GobTest1{17, &StringStruct{"ABC"}})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := &GobTest2{}
 	err = dec.Decode(x)
 	if err == nil {
 		t.Fatal("expected decode error for mismatched fields (encoder to non-decoder)")
 	}
 	if strings.Index(err.String(), "type") < 0 {
 		t.Fatal("expected type error; got", err)
 	}
 	// Non-encoder to GobDecoder: error
 	b.Reset()
 	err = enc.Encode(GobTest2{17, "ABC"})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	y := &GobTest1{}
 	err = dec.Decode(y)
 	if err == nil {
 		t.Fatal("expected decode error for mismatched fields (non-encoder to decoder)")
 	}
 	if strings.Index(err.String(), "type") < 0 {
 		t.Fatal("expected type error; got", err)
 	}
 }

 // Even though ByteStruct is a struct, it's treated as a singleton at the top level.
 func TestGobEncoderStructSingleton(t *testing.T) {
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
 	err := enc.Encode(&ByteStruct{'A'})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(ByteStruct)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if x.a != 'A' {
 		t.Errorf("expected 'A' got %c", x.a)
 	}
 }

 func TestGobEncoderNonStructSingleton(t *testing.T) {
 	b := new(bytes.Buffer)
 	enc := NewEncoder(b)
 	err := enc.Encode(Gobber(1234))
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	var x Gobber
 	err = dec.Decode(&x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if x != 1234 {
 		t.Errorf("expected 1234 got %c", x)
 	}
 }

 func TestGobEncoderIgnoreStructField(t *testing.T) {
 	b := new(bytes.Buffer)
 	// First a field that's a structure.
 	enc := NewEncoder(b)
 	err := enc.Encode(GobTest0{17, &ByteStruct{'A'}})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(GobTestIgnoreEncoder)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if x.X != 17 {
 		t.Errorf("expected 17 got %c", x.X)
 	}
 }

 func TestGobEncoderIgnoreNonStructField(t *testing.T) {
 	b := new(bytes.Buffer)
 	// First a field that's a structure.
 	enc := NewEncoder(b)
 	gobber := Gobber(23)
 	err := enc.Encode(GobTest3{17, &gobber})
 	if err != nil {
 		t.Fatal("encode error:", err)
 	}
 	dec := NewDecoder(b)
 	x := new(GobTestIgnoreEncoder)
 	err = dec.Decode(x)
 	if err != nil {
 		t.Fatal("decode error:", err)
 	}
 	if x.X != 17 {
 		t.Errorf("expected 17 got %c", x.X)
 	}
 }
	// Copyright 20011 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// This file contains tests of the GobEncoder/GobDecoder support.

	package gob

	import (
	"bytes"
	"fmt"
	"os"
	"strings"
	"testing"
	)

	// Types that implement the GobEncoder/Decoder interfaces.

	type ByteStruct struct {
	a byte // not an exported field
	}

	type StringStruct struct {
	s string // not an exported field
	}

	type ArrayStruct struct {
	a [8192]byte // not an exported field
	}

	type Gobber int

	type ValueGobber string // encodes with a value, decodes with a pointer.

	// The relevant methods

	func (g *ByteStruct) GobEncode() ([]byte, os.Error) {
	b := make([]byte, 3)
	b[0] = g.a
	b[1] = g.a + 1
	b[2] = g.a + 2
	return b, nil
	}

	func (g *ByteStruct) GobDecode(data []byte) os.Error {
	if g == nil {
	return os.NewError("NIL RECEIVER")
	}
	// Expect N sequential-valued bytes.
	if len(data) == 0 {
	return os.EOF
	}
	g.a = data[0]
	for i, c := range data {
	if c != g.a+byte(i) {
	return os.NewError("invalid data sequence")
	}
	}
	return nil
	}

	func (g *StringStruct) GobEncode() ([]byte, os.Error) {
	return []byte(g.s), nil
	}

	func (g *StringStruct) GobDecode(data []byte) os.Error {
	// Expect N sequential-valued bytes.
	if len(data) == 0 {
	return os.EOF
	}
	a := data[0]
	for i, c := range data {
	if c != a+byte(i) {
	return os.NewError("invalid data sequence")
	}
	}
	g.s = string(data)
	return nil
	}

	func (a *ArrayStruct) GobEncode() ([]byte, os.Error) {
	return a.a[:], nil
	}

	func (a *ArrayStruct) GobDecode(data []byte) os.Error {
	if len(data) != len(a.a) {
	return os.NewError("wrong length in array decode")
	}
	copy(a.a[:], data)
	return nil
	}

	func (g *Gobber) GobEncode() ([]byte, os.Error) {
	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
	}

	func (g *Gobber) GobDecode(data []byte) os.Error {
	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
	return err
	}

	func (v ValueGobber) GobEncode() ([]byte, os.Error) {
	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
	}

	func (v *ValueGobber) GobDecode(data []byte) os.Error {
	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
	return err
	}

	// Structs that include GobEncodable fields.

	type GobTest0 struct {
	X int // guarantee we have something in common with GobTest*
	G *ByteStruct
	}

	type GobTest1 struct {
	X int // guarantee we have something in common with GobTest*
	G *StringStruct
	}

	type GobTest2 struct {
	X int // guarantee we have something in common with GobTest*
	G string // not a GobEncoder - should give us errors
	}

	type GobTest3 struct {
	X int // guarantee we have something in common with GobTest*
	G *Gobber
	}

	type GobTest4 struct {
	X int // guarantee we have something in common with GobTest*
	V ValueGobber
	}

	type GobTest5 struct {
	X int // guarantee we have something in common with GobTest*
	V *ValueGobber
	}

	type GobTestIgnoreEncoder struct {
	X int // guarantee we have something in common with GobTest*
	}

	type GobTestValueEncDec struct {
	X int // guarantee we have something in common with GobTest*
	G StringStruct // not a pointer.
	}

	type GobTestIndirectEncDec struct {
	X int // guarantee we have something in common with GobTest*
	G ***StringStruct // indirections to the receiver.
	}

	type GobTestArrayEncDec struct {
	X int // guarantee we have something in common with GobTest*
	A ArrayStruct // not a pointer.
	}

	type GobTestIndirectArrayEncDec struct {
	X int // guarantee we have something in common with GobTest*
	A ***ArrayStruct // indirections to a large receiver.
	}

	func TestGobEncoderField(t *testing.T) {
	b := new(bytes.Buffer)
	// First a field that's a structure.
	enc := NewEncoder(b)
	err := enc.Encode(GobTest0{17, &ByteStruct{'A'}})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTest0)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if x.G.a != 'A' {
	t.Errorf("expected 'A' got %c", x.G.a)
	}
	// Now a field that's not a structure.
	b.Reset()
	gobber := Gobber(23)
	err = enc.Encode(GobTest3{17, &gobber})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	y := new(GobTest3)
	err = dec.Decode(y)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if *y.G != 23 {
	t.Errorf("expected '23 got %d", *y.G)
	}
	}

	// Even though the field is a value, we can still take its address
	// and should be able to call the methods.
	func TestGobEncoderValueField(t *testing.T) {
	b := new(bytes.Buffer)
	// First a field that's a structure.
	enc := NewEncoder(b)
	err := enc.Encode(GobTestValueEncDec{17, StringStruct{"HIJKL"}})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTestValueEncDec)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if x.G.s != "HIJKL" {
	t.Errorf("expected `HIJKL` got %s", x.G.s)
	}
	}

	// GobEncode/Decode should work even if the value is
	// more indirect than the receiver.
	func TestGobEncoderIndirectField(t *testing.T) {
	b := new(bytes.Buffer)
	// First a field that's a structure.
	enc := NewEncoder(b)
	s := &StringStruct{"HIJKL"}
	sp := &s
	err := enc.Encode(GobTestIndirectEncDec{17, &sp})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTestIndirectEncDec)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if (***x.G).s != "HIJKL" {
	t.Errorf("expected `HIJKL` got %s", (***x.G).s)
	}
	}

	// Test with a large field with methods.
	func TestGobEncoderArrayField(t *testing.T) {
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	var a GobTestArrayEncDec
	a.X = 17
	for i := range a.A.a {
	a.A.a[i] = byte(i)
	}
	err := enc.Encode(a)
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTestArrayEncDec)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	for i, v := range x.A.a {
	if v != byte(i) {
	t.Errorf("expected %x got %x", byte(i), v)
	break
	}
	}
	}

	// Test an indirection to a large field with methods.
	func TestGobEncoderIndirectArrayField(t *testing.T) {
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	var a GobTestIndirectArrayEncDec
	a.X = 17
	var array ArrayStruct
	ap := &array
	app := &ap
	a.A = &app
	for i := range array.a {
	array.a[i] = byte(i)
	}
	err := enc.Encode(a)
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTestIndirectArrayEncDec)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	for i, v := range (***x.A).a {
	if v != byte(i) {
	t.Errorf("expected %x got %x", byte(i), v)
	break
	}
	}
	}

	// As long as the fields have the same name and implement the
	// interface, we can cross-connect them. Not sure it's useful
	// and may even be bad but it works and it's hard to prevent
	// without exposing the contents of the object, which would
	// defeat the purpose.
	func TestGobEncoderFieldsOfDifferentType(t *testing.T) {
	// first, string in field to byte in field
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	err := enc.Encode(GobTest1{17, &StringStruct{"ABC"}})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTest0)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if x.G.a != 'A' {
	t.Errorf("expected 'A' got %c", x.G.a)
	}
	// now the other direction, byte in field to string in field
	b.Reset()
	err = enc.Encode(GobTest0{17, &ByteStruct{'X'}})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	y := new(GobTest1)
	err = dec.Decode(y)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if y.G.s != "XYZ" {
	t.Fatalf("expected `XYZ` got %c", y.G.s)
	}
	}

	// Test that we can encode a value and decode into a pointer.
	func TestGobEncoderValueEncoder(t *testing.T) {
	// first, string in field to byte in field
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	err := enc.Encode(GobTest4{17, ValueGobber("hello")})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTest5)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if *x.V != "hello" {
	t.Errorf("expected `hello` got %s", x.V)
	}
	}

	func TestGobEncoderFieldTypeError(t *testing.T) {
	// GobEncoder to non-decoder: error
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	err := enc.Encode(GobTest1{17, &StringStruct{"ABC"}})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := &GobTest2{}
	err = dec.Decode(x)
	if err == nil {
	t.Fatal("expected decode error for mismatched fields (encoder to non-decoder)")
	}
	if strings.Index(err.String(), "type") < 0 {
	t.Fatal("expected type error; got", err)
	}
	// Non-encoder to GobDecoder: error
	b.Reset()
	err = enc.Encode(GobTest2{17, "ABC"})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	y := &GobTest1{}
	err = dec.Decode(y)
	if err == nil {
	t.Fatal("expected decode error for mismatched fields (non-encoder to decoder)")
	}
	if strings.Index(err.String(), "type") < 0 {
	t.Fatal("expected type error; got", err)
	}
	}

	// Even though ByteStruct is a struct, it's treated as a singleton at the top level.
	func TestGobEncoderStructSingleton(t *testing.T) {
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	err := enc.Encode(&ByteStruct{'A'})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(ByteStruct)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if x.a != 'A' {
	t.Errorf("expected 'A' got %c", x.a)
	}
	}

	func TestGobEncoderNonStructSingleton(t *testing.T) {
	b := new(bytes.Buffer)
	enc := NewEncoder(b)
	err := enc.Encode(Gobber(1234))
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	var x Gobber
	err = dec.Decode(&x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if x != 1234 {
	t.Errorf("expected 1234 got %c", x)
	}
	}

	func TestGobEncoderIgnoreStructField(t *testing.T) {
	b := new(bytes.Buffer)
	// First a field that's a structure.
	enc := NewEncoder(b)
	err := enc.Encode(GobTest0{17, &ByteStruct{'A'}})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTestIgnoreEncoder)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if x.X != 17 {
	t.Errorf("expected 17 got %c", x.X)
	}
	}

	func TestGobEncoderIgnoreNonStructField(t *testing.T) {
	b := new(bytes.Buffer)
	// First a field that's a structure.
	enc := NewEncoder(b)
	gobber := Gobber(23)
	err := enc.Encode(GobTest3{17, &gobber})
	if err != nil {
	t.Fatal("encode error:", err)
	}
	dec := NewDecoder(b)
	x := new(GobTestIgnoreEncoder)
	err = dec.Decode(x)
	if err != nil {
	t.Fatal("decode error:", err)
	}
	if x.X != 17 {
	t.Errorf("expected 17 got %c", x.X)
	}
	}