Merge 2aeb2555fa into 5f8888e116

accounts/abi/abi.go

@@ -89,7 +89,7 @@ func (abi ABI) Unpack(v interface{}, name string, output []byte) (err error) {
 	} else if event, ok := abi.Events[name]; ok {
 		unpack = event
 	} else {
-		return fmt.Errorf("abi: could not locate named method or event.")
+		return fmt.Errorf("abi: could not locate named method or event")
 	}
 
 	// requires a struct to unpack into for a tuple return...
@@ -99,6 +99,7 @@ func (abi ABI) Unpack(v interface{}, name string, output []byte) (err error) {
 	return unpack.singleUnpack(v, output)
 }
 
+// UnmarshalJSON implements json.Unmarshaler interface
 func (abi *ABI) UnmarshalJSON(data []byte) error {
 	var fields []struct {
 		Type      string

accounts/abi/argument.go

@@ -29,6 +29,7 @@ type Argument struct {
 	Indexed bool // indexed is only used by events
 }
 
+// UnmarshalJSON implements json.Unmarshaler interface
 func (a *Argument) UnmarshalJSON(data []byte) error {
 	var extarg struct {
 		Name    string
@@ -49,3 +50,13 @@ func (a *Argument) UnmarshalJSON(data []byte) error {
 
 	return nil
 }
+
+func countNonIndexedArguments(args []Argument) int {
+	out := 0
+	for i := range args {
+		if !args[i].Indexed {
+			out++
+		}
+	}
+	return out
+}

accounts/abi/event.go

@@ -59,19 +59,22 @@ func (e Event) tupleUnpack(v interface{}, output []byte) error {
 	var (
 		value = valueOf.Elem()
 		typ   = value.Type()
+		kind  = value.Kind()
 	)
-
+	if err := requireUnpackKind(value, typ, kind, e.Inputs, true); err != nil {
-	if value.Kind() != reflect.Struct {
+		return err
-		return fmt.Errorf("abi: cannot unmarshal tuple in to %v", typ)
 	}
 
-	j := 0
+	// `i` counts the nonindexed arguments.
-	for i := 0; i < len(e.Inputs); i++ {
+	// `j` counts the number of complex types.
-		input := e.Inputs[i]
+	// both `i` and `j` are used to to correctly compute `data` offset.
+	i, j := -1, 0
+	for _, input := range e.Inputs {
 		if input.Indexed {
-			// can't read, continue
+			// Indexed arguments are not packed into data
 			continue
 		}
+		i++
 		marshalledValue, err := toGoType((i+j)*32, input.Type, output)
 		if err != nil {
 			return err
@@ -83,31 +86,25 @@ func (e Event) tupleUnpack(v interface{}, output []byte) error {
 		}
 		reflectValue := reflect.ValueOf(marshalledValue)
 
-		switch value.Kind() {
+		switch kind {
 		case reflect.Struct:
 			for j := 0; j < typ.NumField(); j++ {
 				field := typ.Field(j)
 				// TODO read tags: `abi:"fieldName"`
-				if field.Name == strings.ToUpper(e.Inputs[i].Name[:1])+e.Inputs[i].Name[1:] {
+				if field.Name == strings.ToUpper(input.Name[:1])+input.Name[1:] {
-					if err := set(value.Field(j), reflectValue, e.Inputs[i]); err != nil {
+					if err := set(value.Field(j), reflectValue, input); err != nil {
 						return err
 					}
 				}
 			}
 		case reflect.Slice, reflect.Array:
-			if value.Len() < i {
-				return fmt.Errorf("abi: insufficient number of arguments for unpack, want %d, got %d", len(e.Inputs), value.Len())
-			}
 			v := value.Index(i)
-			if v.Kind() != reflect.Ptr && v.Kind() != reflect.Interface {
+			if err := requireAssignable(v, reflectValue); err != nil {
-				return fmt.Errorf("abi: cannot unmarshal %v in to %v", v.Type(), reflectValue.Type())
+				return err
-			}
+			}
-			reflectValue := reflect.ValueOf(marshalledValue)
+			if err := set(v.Elem(), reflectValue, input); err != nil {
-			if err := set(v.Elem(), reflectValue, e.Inputs[i]); err != nil {
 				return err
 			}
-		default:
-			return fmt.Errorf("abi: cannot unmarshal tuple in to %v", typ)
 		}
 	}
 	return nil
@@ -123,7 +120,7 @@ func (e Event) singleUnpack(v interface{}, output []byte) error {
 	}
 
 	if e.Inputs[0].Indexed {
-		return fmt.Errorf("abi: attempting to unpack indexed variable into element.")
+		return fmt.Errorf("abi: attempting to unpack indexed variable into element")
 	}
 
 	value := valueOf.Elem()
@@ -132,8 +129,5 @@ func (e Event) singleUnpack(v interface{}, output []byte) error {
 	if err != nil {
 		return err
 	}
-	if err := set(value, reflect.ValueOf(marshalledValue), e.Inputs[0]); err != nil {
+	return set(value, reflect.ValueOf(marshalledValue), e.Inputs[0])
-		return err
-	}
-	return nil
 }

accounts/abi/event_test.go

@@ -18,15 +18,52 @@ package abi
 
 import (
 	"bytes"
+	"encoding/hex"
+	"encoding/json"
+	"math/big"
 	"reflect"
 	"strings"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+var jsonEventTransfer = []byte(`{
+  "anonymous": false,
+  "inputs": [
+    {
+      "indexed": true, "name": "from", "type": "address"
+    }, {
+      "indexed": true, "name": "to", "type": "address"
+    }, {
+      "indexed": false, "name": "value", "type": "uint256"
+  }],
+  "name": "Transfer",
+  "type": "event"
+}`)
+
+var jsonEventPledge = []byte(`{
+  "anonymous": false,
+  "inputs": [{
+      "indexed": false, "name": "who", "type": "address"
+    }, {
+      "indexed": false, "name": "wad", "type": "uint128"
+    }, {
+      "indexed": false, "name": "currency", "type": "bytes3"
+  }],
+  "name": "Pledge",
+  "type": "event"
+}`)
+
+// 1000000
+var transferData1 = "00000000000000000000000000000000000000000000000000000000000f4240"
+
+// "0x00Ce0d46d924CC8437c806721496599FC3FFA268", 2218516807680, "usd"
+var pledgeData1 = "00000000000000000000000000ce0d46d924cc8437c806721496599fc3ffa2680000000000000000000000000000000000000000000000000000020489e800007573640000000000000000000000000000000000000000000000000000000000"
+
 func TestEventId(t *testing.T) {
 	var table = []struct {
 		definition   string
@@ -77,3 +114,130 @@ func TestEventMultiValueWithArrayUnpack(t *testing.T) {
 	require.Equal(t, [2]uint8{1, 2}, rst.Value1)
 	require.Equal(t, uint8(3), rst.Value2)
 }
+
+func TestEventTupleUnpack(t *testing.T) {
+
+	type EventTransfer struct {
+		Value *big.Int
+	}
+
+	type EventPledge struct {
+		Who      common.Address
+		Wad      *big.Int
+		Currency [3]byte
+	}
+
+	type BadEventPledge struct {
+		Who      string
+		Wad      int
+		Currency [3]byte
+	}
+
+	bigint := new(big.Int)
+	bigintExpected := big.NewInt(1000000)
+	bigintExpected2 := big.NewInt(2218516807680)
+	addr := common.HexToAddress("0x00Ce0d46d924CC8437c806721496599FC3FFA268")
+	var testCases = []struct {
+		data     string
+		dest     interface{}
+		expected interface{}
+		jsonLog  []byte
+		error    string
+		name     string
+	}{{
+		transferData1,
+		&EventTransfer{},
+		&EventTransfer{Value: bigintExpected},
+		jsonEventTransfer,
+		"",
+		"Can unpack ERC20 Transfer event into structure",
+	}, {
+		transferData1,
+		&[]interface{}{&bigint},
+		&[]interface{}{&bigintExpected},
+		jsonEventTransfer,
+		"",
+		"Can unpack ERC20 Transfer event into slice",
+	}, {
+		pledgeData1,
+		&EventPledge{},
+		&EventPledge{
+			addr,
+			bigintExpected2,
+			[3]byte{'u', 's', 'd'}},
+		jsonEventPledge,
+		"",
+		"Can unpack Pledge event into structure",
+	}, {
+		pledgeData1,
+		&[]interface{}{&common.Address{}, &bigint, &[3]byte{}},
+		&[]interface{}{
+			&addr,
+			&bigintExpected2,
+			&[3]byte{'u', 's', 'd'}},
+		jsonEventPledge,
+		"",
+		"Can unpack Pledge event into slice",
+	}, {
+		pledgeData1,
+		&[3]interface{}{&common.Address{}, &bigint, &[3]byte{}},
+		&[3]interface{}{
+			&addr,
+			&bigintExpected2,
+			&[3]byte{'u', 's', 'd'}},
+		jsonEventPledge,
+		"",
+		"Can unpack Pledge event into an array",
+	}, {
+		pledgeData1,
+		&[]interface{}{new(int), 0, 0},
+		&[]interface{}{},
+		jsonEventPledge,
+		"abi: cannot unmarshal common.Address in to int",
+		"Can not unpack Pledge event into slice with wrong types",
+	}, {
+		pledgeData1,
+		&BadEventPledge{},
+		&BadEventPledge{},
+		jsonEventPledge,
+		"abi: cannot unmarshal common.Address in to string",
+		"Can not unpack Pledge event into struct with wrong filed types",
+	}, {
+		pledgeData1,
+		&[]interface{}{common.Address{}, new(big.Int)},
+		&[]interface{}{},
+		jsonEventPledge,
+		"abi: insufficient number of elements in the list/array for unpack, want 3, got 2",
+		"Can not unpack Pledge event into too short slice",
+	}, {
+		pledgeData1,
+		new(map[string]interface{}),
+		&[]interface{}{},
+		jsonEventPledge,
+		"abi: cannot unmarshal tuple into map[string]interface {}",
+		"Can not unpack Pledge event into map",
+	}}
+
+	for _, tc := range testCases {
+		assert := assert.New(t)
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			err := unpackTestEventData(tc.dest, tc.data, tc.jsonLog, assert)
+			if tc.error == "" {
+				assert.Nil(err, "Should be able to unpack event data.")
+				assert.Equal(tc.expected, tc.dest)
+			} else {
+				assert.EqualError(err, tc.error)
+			}
+		})
+	}
+}
+
+func unpackTestEventData(dest interface{}, hexData string, jsonEvent []byte, assert *assert.Assertions) error {
+	data, err := hex.DecodeString(hexData)
+	assert.NoError(err, "Hex data should be a correct hex-string")
+	var e Event
+	assert.NoError(json.Unmarshal(jsonEvent, &e), "Should be able to unmarshal event ABI")
+	a := ABI{Events: map[string]Event{"e": e}}
+	return a.Unpack(dest, "e", data)
+}

accounts/abi/method.go

@@ -24,7 +24,7 @@ import (
 	"github.com/ethereum/go-ethereum/crypto"
 )
 
-// Callable method given a `Name` and whether the method is a constant.
+// Method represents a callable given a `Name` and whether the method is a constant.
 // If the method is `Const` no transaction needs to be created for this
 // particular Method call. It can easily be simulated using a local VM.
 // For example a `Balance()` method only needs to retrieve something
@@ -91,7 +91,7 @@ func (method Method) pack(args ...interface{}) ([]byte, error) {
 // unpacks a method return tuple into a struct of corresponding go types
 //
 // Unpacking can be done into a struct or a slice/array.
-func (method Method) tupleUnpack(v interface{}, output []byte) error {
+func (method Method) tupleUnpack(v interface{}, outputSlice []byte) error {
 	// make sure the passed value is a pointer
 	valueOf := reflect.ValueOf(v)
 	if reflect.Ptr != valueOf.Kind() {
@@ -101,47 +101,44 @@ func (method Method) tupleUnpack(v interface{}, output []byte) error {
 	var (
 		value = valueOf.Elem()
 		typ   = value.Type()
+		kind  = value.Kind()
 	)
+	if err := requireUnpackKind(value, typ, kind, method.Outputs, false); err != nil {
+		return err
+	}
 
 	j := 0
-	for i := 0; i < len(method.Outputs); i++ {
+	for i, output := range method.Outputs {
-		toUnpack := method.Outputs[i]
+		marshalledValue, err := toGoType((i+j)*32, output.Type, outputSlice)
-		marshalledValue, err := toGoType((i+j)*32, toUnpack.Type, output)
 		if err != nil {
 			return err
 		}
-		if toUnpack.Type.T == ArrayTy {
+		if output.Type.T == ArrayTy {
 			// combined index ('i' + 'j') need to be adjusted only by size of array, thus
 			// we need to decrement 'j' because 'i' was incremented
-			j += toUnpack.Type.Size - 1
+			j += output.Type.Size - 1
 		}
 		reflectValue := reflect.ValueOf(marshalledValue)
 
-		switch value.Kind() {
+		switch kind {
 		case reflect.Struct:
 			for j := 0; j < typ.NumField(); j++ {
 				field := typ.Field(j)
 				// TODO read tags: `abi:"fieldName"`
-				if field.Name == strings.ToUpper(method.Outputs[i].Name[:1])+method.Outputs[i].Name[1:] {
+				if field.Name == strings.ToUpper(output.Name[:1])+output.Name[1:] {
-					if err := set(value.Field(j), reflectValue, method.Outputs[i]); err != nil {
+					if err := set(value.Field(j), reflectValue, output); err != nil {
 						return err
 					}
 				}
 			}
 		case reflect.Slice, reflect.Array:
-			if value.Len() < i {
-				return fmt.Errorf("abi: insufficient number of arguments for unpack, want %d, got %d", len(method.Outputs), value.Len())
-			}
 			v := value.Index(i)
-			if v.Kind() != reflect.Ptr && v.Kind() != reflect.Interface {
+			if err := requireAssignable(v, reflectValue); err != nil {
-				return fmt.Errorf("abi: cannot unmarshal %v in to %v", v.Type(), reflectValue.Type())
+				return err
-			}
+			}
-			reflectValue := reflect.ValueOf(marshalledValue)
+			if err := set(v.Elem(), reflectValue, output); err != nil {
-			if err := set(v.Elem(), reflectValue, method.Outputs[i]); err != nil {
 				return err
 			}
-		default:
-			return fmt.Errorf("abi: cannot unmarshal tuple in to %v", typ)
 		}
 	}
 	return nil
@@ -162,10 +159,7 @@ func (method Method) singleUnpack(v interface{}, output []byte) error {
 	if err != nil {
 		return err
 	}
-	if err := set(value, reflect.ValueOf(marshalledValue), method.Outputs[0]); err != nil {
+	return set(value, reflect.ValueOf(marshalledValue), method.Outputs[0])
-		return err
-	}
-	return nil
 }
 
 // Sig returns the methods string signature according to the ABI spec.
@@ -175,35 +169,35 @@ func (method Method) singleUnpack(v interface{}, output []byte) error {
 //     function foo(uint32 a, int b)    =    "foo(uint32,int256)"
 //
 // Please note that "int" is substitute for its canonical representation "int256"
-func (m Method) Sig() string {
+func (method Method) Sig() string {
-	types := make([]string, len(m.Inputs))
+	types := make([]string, len(method.Inputs))
 	i := 0
-	for _, input := range m.Inputs {
+	for _, input := range method.Inputs {
 		types[i] = input.Type.String()
 		i++
 	}
-	return fmt.Sprintf("%v(%v)", m.Name, strings.Join(types, ","))
+	return fmt.Sprintf("%v(%v)", method.Name, strings.Join(types, ","))
 }
 
-func (m Method) String() string {
+func (method Method) String() string {
-	inputs := make([]string, len(m.Inputs))
+	inputs := make([]string, len(method.Inputs))
-	for i, input := range m.Inputs {
+	for i, input := range method.Inputs {
 		inputs[i] = fmt.Sprintf("%v %v", input.Name, input.Type)
 	}
-	outputs := make([]string, len(m.Outputs))
+	outputs := make([]string, len(method.Outputs))
-	for i, output := range m.Outputs {
+	for i, output := range method.Outputs {
 		if len(output.Name) > 0 {
 			outputs[i] = fmt.Sprintf("%v ", output.Name)
 		}
 		outputs[i] += output.Type.String()
 	}
 	constant := ""
-	if m.Const {
+	if method.Const {
 		constant = "constant "
 	}
-	return fmt.Sprintf("function %v(%v) %sreturns(%v)", m.Name, strings.Join(inputs, ", "), constant, strings.Join(outputs, ", "))
+	return fmt.Sprintf("function %v(%v) %sreturns(%v)", method.Name, strings.Join(inputs, ", "), constant, strings.Join(outputs, ", "))
 }
 
-func (m Method) Id() []byte {
+func (method Method) Id() []byte {
-	return crypto.Keccak256([]byte(m.Sig()))[:4]
+	return crypto.Keccak256([]byte(method.Sig()))[:4]
 }

accounts/abi/pack.go

@@ -48,9 +48,8 @@ func packElement(t Type, reflectValue reflect.Value) []byte {
 	case BoolTy:
 		if reflectValue.Bool() {
 			return math.PaddedBigBytes(common.Big1, 32)
-		} else {
-			return math.PaddedBigBytes(common.Big0, 32)
 		}
+		return math.PaddedBigBytes(common.Big0, 32)
 	case BytesTy:
 		if reflectValue.Kind() == reflect.Array {
 			reflectValue = mustArrayToByteSlice(reflectValue)

accounts/abi/reflect.go

@@ -85,3 +85,32 @@ func set(dst, src reflect.Value, output Argument) error {
 	}
 	return nil
 }
+
+// requireUnpackKind verifies preconditions for unpacking `args` into `kind`
+func requireUnpackKind(v reflect.Value, t reflect.Type, k reflect.Kind,
+	args []Argument, ignoreIndexed bool) error {
+
+	switch k {
+	case reflect.Struct:
+	case reflect.Slice, reflect.Array:
+		minLen := len(args)
+		if ignoreIndexed {
+			minLen = countNonIndexedArguments(args)
+		}
+		if v.Len() < minLen {
+			return fmt.Errorf("abi: insufficient number of elements in the list/array for unpack, want %d, got %d",
+				minLen, v.Len())
+		}
+	default:
+		return fmt.Errorf("abi: cannot unmarshal tuple into %v", t)
+	}
+	return nil
+}
+
+// requireAssignable assures that `dest` is a pointer and it's not an interface.
+func requireAssignable(dst, src reflect.Value) error {
+	if dst.Kind() != reflect.Ptr && dst.Kind() != reflect.Interface {
+		return fmt.Errorf("abi: cannot unmarshal %v into %v", src.Type(), dst.Type())
+	}
+	return nil
+}

accounts/abi/type.go

@@ -24,6 +24,7 @@ import (
 	"strings"
 )
 
+// Type enumerator
 const (
 	IntTy byte = iota
 	UintTy
@@ -100,7 +101,7 @@ func NewType(t string) (typ Type, err error) {
 			return Type{}, fmt.Errorf("invalid formatting of array type")
 		}
 		return typ, err
-	} else {
+	}
 	// parse the type and size of the abi-type.
 	parsedType := typeRegex.FindAllStringSubmatch(t, -1)[0]
 	// varSize is the size of the variable
@@ -119,9 +120,7 @@ func NewType(t string) (typ Type, err error) {
 		}
 	}
 	// varType is the parsed abi type
-		varType := parsedType[1]
+	switch varType := parsedType[1]; varType {
-
-		switch varType {
 	case "int":
 		typ.Kind, typ.Type = reflectIntKindAndType(false, varSize)
 		typ.Size = varSize
@@ -162,7 +161,6 @@ func NewType(t string) (typ Type, err error) {
 	default:
 		return Type{}, fmt.Errorf("unsupported arg type: %s", t)
 	}
-	}
 
 	return
 }

accounts/abi/unpack.go

@@ -79,7 +79,7 @@ func readBool(word []byte) (bool, error) {
 // This enforces that standard by always presenting it as a 24-array (address + sig = 24 bytes)
 func readFunctionType(t Type, word []byte) (funcTy [24]byte, err error) {
 	if t.T != FunctionTy {
-		return [24]byte{}, fmt.Errorf("abi: invalid type in call to make function type byte array.")
+		return [24]byte{}, fmt.Errorf("abi: invalid type in call to make function type byte array")
 	}
 	if garbage := binary.BigEndian.Uint64(word[24:32]); garbage != 0 {
 		err = fmt.Errorf("abi: got improperly encoded function type, got %v", word)
@@ -92,7 +92,7 @@ func readFunctionType(t Type, word []byte) (funcTy [24]byte, err error) {
 // through reflection, creates a fixed array to be read from
 func readFixedBytes(t Type, word []byte) (interface{}, error) {
 	if t.T != FixedBytesTy {
-		return nil, fmt.Errorf("abi: invalid type in call to make fixed byte array.")
+		return nil, fmt.Errorf("abi: invalid type in call to make fixed byte array")
 	}
 	// convert
 	array := reflect.New(t.Type).Elem()

accounts/abi/unpack_test.go

@@ -27,6 +27,7 @@ import (
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/stretchr/testify/require"
 )
 
 type unpackTest struct {
@@ -286,56 +287,83 @@ func TestUnpack(t *testing.T) {
 	}
 }
 
-func TestMultiReturnWithStruct(t *testing.T) {
+type methodMultiOutput struct {
-	const definition = `[
+	Int    *big.Int
-	{ "name" : "multi", "constant" : false, "outputs": [ { "name": "Int", "type": "uint256" }, { "name": "String", "type": "string" } ] }]`
+	String string
-
-	abi, err := JSON(strings.NewReader(definition))
-	if err != nil {
-		t.Fatal(err)
 }
 
+func methodMultiReturn(require *require.Assertions) (ABI, []byte, methodMultiOutput) {
+	const definition = `[
+	{ "name" : "multi", "constant" : false, "outputs": [ { "name": "Int", "type": "uint256" }, { "name": "String", "type": "string" } ] }]`
+	var expected = methodMultiOutput{big.NewInt(1), "hello"}
+
+	abi, err := JSON(strings.NewReader(definition))
+	require.NoError(err)
 	// using buff to make the code readable
 	buff := new(bytes.Buffer)
 	buff.Write(common.Hex2Bytes("0000000000000000000000000000000000000000000000000000000000000001"))
 	buff.Write(common.Hex2Bytes("0000000000000000000000000000000000000000000000000000000000000040"))
 	buff.Write(common.Hex2Bytes("0000000000000000000000000000000000000000000000000000000000000005"))
-	stringOut := "hello"
+	buff.Write(common.RightPadBytes([]byte(expected.String), 32))
-	buff.Write(common.RightPadBytes([]byte(stringOut), 32))
+	return abi, buff.Bytes(), expected
-
-	var inter struct {
-		Int    *big.Int
-		String string
-	}
-	err = abi.Unpack(&inter, "multi", buff.Bytes())
-	if err != nil {
-		t.Error(err)
 }
 
-	if inter.Int == nil || inter.Int.Cmp(big.NewInt(1)) != 0 {
+func TestMethodMultiReturn(t *testing.T) {
-		t.Error("expected Int to be 1 got", inter.Int)
+	type reversed struct {
-	}
-
-	if inter.String != stringOut {
-		t.Error("expected String to be", stringOut, "got", inter.String)
-	}
-
-	var reversed struct {
 		String string
 		Int    *big.Int
 	}
 
-	err = abi.Unpack(&reversed, "multi", buff.Bytes())
+	abi, data, expected := methodMultiReturn(require.New(t))
-	if err != nil {
+	bigint := new(big.Int)
-		t.Error(err)
+	var testCases = []struct {
+		dest     interface{}
+		expected interface{}
+		error    string
+		name     string
+	}{{
+		&methodMultiOutput{},
+		&expected,
+		"",
+		"Can unpack into structure",
+	}, {
+		&reversed{},
+		&reversed{expected.String, expected.Int},
+		"",
+		"Can unpack into reversed structure",
+	}, {
+		&[]interface{}{&bigint, new(string)},
+		&[]interface{}{&expected.Int, &expected.String},
+		"",
+		"Can unpack into a slice",
+	}, {
+		&[2]interface{}{&bigint, new(string)},
+		&[2]interface{}{&expected.Int, &expected.String},
+		"",
+		"Can unpack into an array",
+	}, {
+		&[]interface{}{new(int), new(int)},
+		&[]interface{}{&expected.Int, &expected.String},
+		"abi: cannot unmarshal *big.Int in to int",
+		"Can not unpack into a slice with wrong types",
+	}, {
+		&[]interface{}{new(int)},
+		&[]interface{}{},
+		"abi: insufficient number of elements in the list/array for unpack, want 2, got 1",
+		"Can not unpack into a slice with wrong types",
+	}}
+	for _, tc := range testCases {
+		tc := tc
+		t.Run(tc.name, func(t *testing.T) {
+			require := require.New(t)
+			err := abi.Unpack(tc.dest, "multi", data)
+			if tc.error == "" {
+				require.Nil(err, "Should be able to unpack method outputs.")
+				require.Equal(tc.expected, tc.dest)
+			} else {
+				require.EqualError(err, tc.error)
 			}
-
+		})
-	if reversed.Int == nil || reversed.Int.Cmp(big.NewInt(1)) != 0 {
-		t.Error("expected Int to be 1 got", reversed.Int)
-	}
-
-	if reversed.String != stringOut {
-		t.Error("expected String to be", stringOut, "got", reversed.String)
 	}
 }