1 files changed, 798 insertions, 0 deletions
diff --git a/src/encoding/gob/gobencdec_test.go b/src/encoding/gob/gobencdec_test.go
new file mode 100644
index 000000000..eb76b481d
--- /dev/null
+++ b/src/encoding/gob/gobencdec_test.go
@@ -0,0 +1,798 @@
+// Copyright 2011 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"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+	"testing"
+	"time"
+)
+
+// 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.
+
+type BinaryGobber int
+
+type BinaryValueGobber string
+
+type TextGobber int
+
+type TextValueGobber string
+
+// The relevant methods
+
+func (g *ByteStruct) GobEncode() ([]byte, 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) error {
+	if g == nil {
+		return errors.New("NIL RECEIVER")
+	}
+	// Expect N sequential-valued bytes.
+	if len(data) == 0 {
+		return io.EOF
+	}
+	g.a = data[0]
+	for i, c := range data {
+		if c != g.a+byte(i) {
+			return errors.New("invalid data sequence")
+		}
+	}
+	return nil
+}
+
+func (g *StringStruct) GobEncode() ([]byte, error) {
+	return []byte(g.s), nil
+}
+
+func (g *StringStruct) GobDecode(data []byte) error {
+	// Expect N sequential-valued bytes.
+	if len(data) == 0 {
+		return io.EOF
+	}
+	a := data[0]
+	for i, c := range data {
+		if c != a+byte(i) {
+			return errors.New("invalid data sequence")
+		}
+	}
+	g.s = string(data)
+	return nil
+}
+
+func (a *ArrayStruct) GobEncode() ([]byte, error) {
+	return a.a[:], nil
+}
+
+func (a *ArrayStruct) GobDecode(data []byte) error {
+	if len(data) != len(a.a) {
+		return errors.New("wrong length in array decode")
+	}
+	copy(a.a[:], data)
+	return nil
+}
+
+func (g *Gobber) GobEncode() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
+}
+
+func (g *Gobber) GobDecode(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
+	return err
+}
+
+func (g *BinaryGobber) MarshalBinary() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
+}
+
+func (g *BinaryGobber) UnmarshalBinary(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
+	return err
+}
+
+func (g *TextGobber) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%d", *g)), nil
+}
+
+func (g *TextGobber) UnmarshalText(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%d", (*int)(g))
+	return err
+}
+
+func (v ValueGobber) GobEncode() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
+}
+
+func (v *ValueGobber) GobDecode(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
+	return err
+}
+
+func (v BinaryValueGobber) MarshalBinary() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
+}
+
+func (v *BinaryValueGobber) UnmarshalBinary(data []byte) error {
+	_, err := fmt.Sscanf(string(data), "VALUE=%s", (*string)(v))
+	return err
+}
+
+func (v TextValueGobber) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("VALUE=%s", v)), nil
+}
+
+func (v *TextValueGobber) UnmarshalText(data []byte) 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
+	B *BinaryGobber
+	T *TextGobber
+}
+
+type GobTest4 struct {
+	X  int // guarantee we have  something in common with GobTest*
+	V  ValueGobber
+	BV BinaryValueGobber
+	TV TextValueGobber
+}
+
+type GobTest5 struct {
+	X  int // guarantee we have  something in common with GobTest*
+	V  *ValueGobber
+	BV *BinaryValueGobber
+	TV *TextValueGobber
+}
+
+type GobTest6 struct {
+	X  int // guarantee we have  something in common with GobTest*
+	V  ValueGobber
+	W  *ValueGobber
+	BV BinaryValueGobber
+	BW *BinaryValueGobber
+	TV TextValueGobber
+	TW *TextValueGobber
+}
+
+type GobTest7 struct {
+	X  int // guarantee we have  something in common with GobTest*
+	V  *ValueGobber
+	W  ValueGobber
+	BV *BinaryValueGobber
+	BW BinaryValueGobber
+	TV *TextValueGobber
+	TW TextValueGobber
+}
+
+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)
+	bgobber := BinaryGobber(24)
+	tgobber := TextGobber(25)
+	err = enc.Encode(GobTest3{17, &gobber, &bgobber, &tgobber})
+	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 || *y.B != 24 || *y.T != 25 {
+		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 %q", 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"), BinaryValueGobber("Καλημέρα"), TextValueGobber("こんにちは")})
+	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" || *x.BV != "Καλημέρα" || *x.TV != "こんにちは" {
+		t.Errorf("expected `hello` got %s", *x.V)
+	}
+}
+
+// Test that we can use a value then a pointer type of a GobEncoder
+// in the same encoded value.  Bug 4647.
+func TestGobEncoderValueThenPointer(t *testing.T) {
+	v := ValueGobber("forty-two")
+	w := ValueGobber("six-by-nine")
+	bv := BinaryValueGobber("1nanocentury")
+	bw := BinaryValueGobber("πseconds")
+	tv := TextValueGobber("gravitationalacceleration")
+	tw := TextValueGobber("π²ft/s²")
+
+	// this was a bug: encoding a GobEncoder by value before a GobEncoder
+	// pointer would cause duplicate type definitions to be sent.
+
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	if err := enc.Encode(GobTest6{42, v, &w, bv, &bw, tv, &tw}); err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTest6)
+	if err := dec.Decode(x); err != nil {
+		t.Fatal("decode error:", err)
+	}
+
+	if got, want := x.V, v; got != want {
+		t.Errorf("v = %q, want %q", got, want)
+	}
+	if got, want := x.W, w; got == nil {
+		t.Errorf("w = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("w = %q, want %q", *got, want)
+	}
+
+	if got, want := x.BV, bv; got != want {
+		t.Errorf("bv = %q, want %q", got, want)
+	}
+	if got, want := x.BW, bw; got == nil {
+		t.Errorf("bw = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("bw = %q, want %q", *got, want)
+	}
+
+	if got, want := x.TV, tv; got != want {
+		t.Errorf("tv = %q, want %q", got, want)
+	}
+	if got, want := x.TW, tw; got == nil {
+		t.Errorf("tw = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("tw = %q, want %q", *got, want)
+	}
+}
+
+// Test that we can use a pointer then a value type of a GobEncoder
+// in the same encoded value.
+func TestGobEncoderPointerThenValue(t *testing.T) {
+	v := ValueGobber("forty-two")
+	w := ValueGobber("six-by-nine")
+	bv := BinaryValueGobber("1nanocentury")
+	bw := BinaryValueGobber("πseconds")
+	tv := TextValueGobber("gravitationalacceleration")
+	tw := TextValueGobber("π²ft/s²")
+
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	if err := enc.Encode(GobTest7{42, &v, w, &bv, bw, &tv, tw}); err != nil {
+		t.Fatal("encode error:", err)
+	}
+	dec := NewDecoder(b)
+	x := new(GobTest7)
+	if err := dec.Decode(x); err != nil {
+		t.Fatal("decode error:", err)
+	}
+
+	if got, want := x.V, v; got == nil {
+		t.Errorf("v = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("v = %q, want %q", *got, want)
+	}
+	if got, want := x.W, w; got != want {
+		t.Errorf("w = %q, want %q", got, want)
+	}
+
+	if got, want := x.BV, bv; got == nil {
+		t.Errorf("bv = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("bv = %q, want %q", *got, want)
+	}
+	if got, want := x.BW, bw; got != want {
+		t.Errorf("bw = %q, want %q", got, want)
+	}
+
+	if got, want := x.TV, tv; got == nil {
+		t.Errorf("tv = nil, want %q", want)
+	} else if *got != want {
+		t.Errorf("tv = %q, want %q", *got, want)
+	}
+	if got, want := x.TW, tw; got != want {
+		t.Errorf("tw = %q, want %q", got, want)
+	}
+}
+
+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.Error(), "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.Error(), "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)
+	var g Gobber = 1234
+	err := enc.Encode(&g)
+	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 %d", 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)
+	bgobber := BinaryGobber(24)
+	tgobber := TextGobber(25)
+	err := enc.Encode(GobTest3{17, &gobber, &bgobber, &tgobber})
+	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 TestGobEncoderIgnoreNilEncoder(t *testing.T) {
+	b := new(bytes.Buffer)
+	// First a field that's a structure.
+	enc := NewEncoder(b)
+	err := enc.Encode(GobTest0{X: 18}) // G is nil
+	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.X != 18 {
+		t.Errorf("expected x.X = 18, got %v", x.X)
+	}
+	if x.G != nil {
+		t.Errorf("expected x.G = nil, got %v", x.G)
+	}
+}
+
+type gobDecoderBug0 struct {
+	foo, bar string
+}
+
+func (br *gobDecoderBug0) String() string {
+	return br.foo + "-" + br.bar
+}
+
+func (br *gobDecoderBug0) GobEncode() ([]byte, error) {
+	return []byte(br.String()), nil
+}
+
+func (br *gobDecoderBug0) GobDecode(b []byte) error {
+	br.foo = "foo"
+	br.bar = "bar"
+	return nil
+}
+
+// This was a bug: the receiver has a different indirection level
+// than the variable.
+func TestGobEncoderExtraIndirect(t *testing.T) {
+	gdb := &gobDecoderBug0{"foo", "bar"}
+	buf := new(bytes.Buffer)
+	e := NewEncoder(buf)
+	if err := e.Encode(gdb); err != nil {
+		t.Fatalf("encode: %v", err)
+	}
+	d := NewDecoder(buf)
+	var got *gobDecoderBug0
+	if err := d.Decode(&got); err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	if got.foo != gdb.foo || got.bar != gdb.bar {
+		t.Errorf("got = %q, want %q", got, gdb)
+	}
+}
+
+// Another bug: this caused a crash with the new Go1 Time type.
+// We throw in a gob-encoding array, to test another case of isZero,
+// and a struct containing an nil interface, to test a third.
+type isZeroBug struct {
+	T time.Time
+	S string
+	I int
+	A isZeroBugArray
+	F isZeroBugInterface
+}
+
+type isZeroBugArray [2]uint8
+
+// Receiver is value, not pointer, to test isZero of array.
+func (a isZeroBugArray) GobEncode() (b []byte, e error) {
+	b = append(b, a[:]...)
+	return b, nil
+}
+
+func (a *isZeroBugArray) GobDecode(data []byte) error {
+	if len(data) != len(a) {
+		return io.EOF
+	}
+	a[0] = data[0]
+	a[1] = data[1]
+	return nil
+}
+
+type isZeroBugInterface struct {
+	I interface{}
+}
+
+func (i isZeroBugInterface) GobEncode() (b []byte, e error) {
+	return []byte{}, nil
+}
+
+func (i *isZeroBugInterface) GobDecode(data []byte) error {
+	return nil
+}
+
+func TestGobEncodeIsZero(t *testing.T) {
+	x := isZeroBug{time.Now(), "hello", -55, isZeroBugArray{1, 2}, isZeroBugInterface{}}
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err := enc.Encode(x)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	var y isZeroBug
+	dec := NewDecoder(b)
+	err = dec.Decode(&y)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if x != y {
+		t.Fatalf("%v != %v", x, y)
+	}
+}
+
+func TestGobEncodePtrError(t *testing.T) {
+	var err error
+	b := new(bytes.Buffer)
+	enc := NewEncoder(b)
+	err = enc.Encode(&err)
+	if err != nil {
+		t.Fatal("encode:", err)
+	}
+	dec := NewDecoder(b)
+	err2 := fmt.Errorf("foo")
+	err = dec.Decode(&err2)
+	if err != nil {
+		t.Fatal("decode:", err)
+	}
+	if err2 != nil {
+		t.Fatalf("expected nil, got %v", err2)
+	}
+}
+
+func TestNetIP(t *testing.T) {
+	// Encoding of net.IP{1,2,3,4} in Go 1.1.
+	enc := []byte{0x07, 0x0a, 0x00, 0x04, 0x01, 0x02, 0x03, 0x04}
+
+	var ip net.IP
+	err := NewDecoder(bytes.NewReader(enc)).Decode(&ip)
+	if err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	if ip.String() != "1.2.3.4" {
+		t.Errorf("decoded to %v, want 1.2.3.4", ip.String())
+	}
+}