[#103] proto: Test end-to-end scenario

Test the generated code, do not write yet another marshaling routine in
tests.

Before:
```
ok      git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/util/proto      0.003s  coverage: 55.6% of statements
```

After:
```
ok      git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/util/proto      0.003s  coverage: 80.0% of statements
```

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

Makefile

@@ -71,6 +71,17 @@ protoc:
 			--go-grpc_out=. --go-grpc_opt=paths=source_relative $$f; \
 	done
 
+protogen:
+	@go build -v -trimpath \
+		-o $(BIN)/protogen \
+		./util/protogen
+
+protoc-test: protoc protogen
+	@$(PROTOC_DIR)/bin/protoc \
+			--plugin=protoc-gen-go-frostfs=$(abspath $(BIN)/protogen) \
+			--go-frostfs_out=. --go-frostfs_opt=paths=source_relative \
+			./util/proto/test/test.proto
+
 # Run Unit Test with go test
 test: GOFLAGS ?= "-count=1"
 test:

util/proto/marshal_test.go

@@ -1,826 +1,155 @@
 package proto_test
 
 import (
-	"encoding/binary"
 	"math"
+	"math/rand"
 	"testing"
 
-	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/util/proto"
 	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/util/proto/test"
 	"github.com/stretchr/testify/require"
-	"google.golang.org/protobuf/encoding/protowire"
 	goproto "google.golang.org/protobuf/proto"
 )
 
-type SomeEnum int32
-
-type stablePrimitives struct {
-	FieldA []byte
-	FieldB string
-	FieldC bool
-	FieldD int32
-	FieldE uint32
-	FieldF int64
-	FieldG uint64
-	FieldH SomeEnum
-	FieldI uint64 // fixed64
-	FieldJ float64
-	FieldK uint32 // fixed32
+type protoInt interface {
+	~int32 | ~uint32 | ~int64 | ~uint64
 }
 
-type stableRepPrimitives struct {
-	FieldA [][]byte
-	FieldB []string
-	FieldC []int32
-	FieldD []uint32
-	FieldE []int64
-	FieldF []uint64
-
-	FieldFu []uint64
+func nonZero[T protoInt]() T {
+	var r T
+	for r == 0 {
+		r = T(rand.Uint64())
+	}
+	return r
 }
 
-const (
-	ENUM_UNKNOWN  SomeEnum = 0
-	ENUM_POSITIVE SomeEnum = 1
-	ENUM_NEGATIVE SomeEnum = -1
-)
-
-func (s *stablePrimitives) stableMarshal(buf []byte, wrongField bool) ([]byte, error) {
-	if s == nil {
-		return []byte{}, nil
-	}
-
-	if buf == nil {
-		buf = make([]byte, s.stableSize())
-	}
-
-	var i, offset, fieldNum int
-
-	fieldNum = 1
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.BytesMarshal(fieldNum, buf, s.FieldA)
-
-	fieldNum = 2
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.StringMarshal(fieldNum, buf, s.FieldB)
-
-	fieldNum = 200
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.BoolMarshal(fieldNum, buf, s.FieldC)
-
-	fieldNum = 201
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.Int32Marshal(fieldNum, buf, s.FieldD)
-
-	fieldNum = 202
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.UInt32Marshal(fieldNum, buf, s.FieldE)
-
-	fieldNum = 203
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.Int64Marshal(fieldNum, buf, s.FieldF)
-
-	fieldNum = 204
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.UInt64Marshal(fieldNum, buf, s.FieldG)
-
-	fieldNum = 205
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.Fixed64Marshal(fieldNum, buf, s.FieldI)
-
-	fieldNum = 206
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.Float64Marshal(fieldNum, buf, s.FieldJ)
-
-	fieldNum = 207
-	if wrongField {
-		fieldNum++
-	}
-
-	offset = proto.Fixed32Marshal(fieldNum, buf, s.FieldK)
-
-	i += offset
-
-	fieldNum = 300
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.EnumMarshal(fieldNum, buf, int32(s.FieldH))
-
-	return buf, nil
-}
-
-func (s *stablePrimitives) stableSize() int {
-	return proto.BytesSize(1, s.FieldA) +
-		proto.StringSize(2, s.FieldB) +
-		proto.BoolSize(200, s.FieldC) +
-		proto.Int32Size(201, s.FieldD) +
-		proto.UInt32Size(202, s.FieldE) +
-		proto.Int64Size(203, s.FieldF) +
-		proto.UInt64Size(204, s.FieldG) +
-		proto.Fixed64Size(205, s.FieldI) +
-		proto.Float64Size(206, s.FieldJ) +
-		proto.Fixed32Size(207, s.FieldK) +
-		proto.EnumSize(300, int32(s.FieldH))
-}
-
-func (s *stableRepPrimitives) stableMarshal(buf []byte, wrongField bool) ([]byte, error) {
-	if s == nil {
-		return []byte{}, nil
-	}
-
-	if buf == nil {
-		buf = make([]byte, s.stableSize())
-	}
-
-	var i, fieldNum int
-
-	fieldNum = 1
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.RepeatedBytesMarshal(fieldNum, buf, s.FieldA)
-
-	fieldNum = 2
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.RepeatedStringMarshal(fieldNum, buf, s.FieldB)
-
-	fieldNum = 3
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.RepeatedInt32Marshal(fieldNum, buf, s.FieldC)
-
-	fieldNum = 4
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.RepeatedUInt32Marshal(fieldNum, buf, s.FieldD)
-
-	fieldNum = 5
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.RepeatedInt64Marshal(fieldNum, buf, s.FieldE)
-
-	fieldNum = 6
-	if wrongField {
-		fieldNum++
-	}
-	i += proto.RepeatedUInt64Marshal(fieldNum, buf, s.FieldF)
-
-	fieldNum = 7
-	if wrongField {
-		fieldNum++
-	}
-	for j := range s.FieldFu {
-		{
-			prefix := protowire.EncodeTag(
-				protowire.Number(fieldNum),
-				protowire.VarintType)
-			i += binary.PutUvarint(buf[i:], uint64(prefix))
-			i += binary.PutUvarint(buf[i:], s.FieldFu[j])
-		}
-	}
-
-	return buf, nil
-}
-
-func (s *stableRepPrimitives) stableSize() int {
-	f1 := proto.RepeatedBytesSize(1, s.FieldA)
-	f2 := proto.RepeatedStringSize(2, s.FieldB)
-	f3, _ := proto.RepeatedInt32Size(3, s.FieldC)
-	f4, _ := proto.RepeatedUInt32Size(4, s.FieldD)
-	f5, _ := proto.RepeatedInt64Size(5, s.FieldE)
-	f6, _ := proto.RepeatedUInt64Size(6, s.FieldF)
-
-	var f7 int
-	for i := range s.FieldFu {
-		f7 += protowire.SizeGroup(protowire.Number(7), protowire.SizeVarint(s.FieldFu[i]))
-	}
-
-	return f1 + f2 + f3 + f4 + f5 + f6 + f7
-}
-
-func TestBytesMarshal(t *testing.T) {
-	t.Run("not empty", func(t *testing.T) {
-		data := []byte("Hello World")
-		testBytesMarshal(t, data, false)
-		testBytesMarshal(t, data, true)
-	})
-
+func TestStableMarshalSingle(t *testing.T) {
 	t.Run("empty", func(t *testing.T) {
-		testBytesMarshal(t, []byte{}, false)
+		input := &test.Primitives{}
+		require.Zero(t, input.StableSize())
+
+		r := input.StableMarshal(nil)
+		require.Empty(t, r)
 	})
 
-	t.Run("nil", func(t *testing.T) {
-		testBytesMarshal(t, nil, false)
+	marshalCases := []struct {
+		name  string
+		input *test.Primitives
+	}{
+		{name: "bytes", input: &test.Primitives{FieldA: []byte{1, 2, 3}}},
+		{name: "string", input: &test.Primitives{FieldB: "123"}},
+		{name: "bool", input: &test.Primitives{FieldC: true}},
+		{name: "int32", input: &test.Primitives{FieldD: nonZero[int32]()}},
+		{name: "uint32", input: &test.Primitives{FieldE: nonZero[uint32]()}},
+		{name: "int64", input: &test.Primitives{FieldF: nonZero[int64]()}},
+		{name: "uint64", input: &test.Primitives{FieldG: nonZero[uint64]()}},
+		{name: "uint64", input: &test.Primitives{FieldI: nonZero[uint64]()}},
+		{name: "float64", input: &test.Primitives{FieldJ: math.Float64frombits(12345677890)}},
+		{name: "fixed32", input: &test.Primitives{FieldK: nonZero[uint32]()}},
+		{name: "enum, positive", input: &test.Primitives{FieldH: test.Primitives_POSITIVE}},
+		{name: "enum, negative", input: &test.Primitives{FieldH: test.Primitives_NEGATIVE}},
+	}
+	for _, tc := range marshalCases {
+		t.Run(tc.name, func(t *testing.T) {
+			r := tc.input.StableMarshal(nil)
+			require.Equal(t, len(r), tc.input.StableSize())
+			require.NotEmpty(t, r)
+
+			var actual test.Primitives
+			require.NoError(t, goproto.Unmarshal(r, &actual))
+
+			// Compare each field directly, because proto-generated code has private fields.
+			require.Equal(t, tc.input.FieldA, actual.FieldA)
+			require.Equal(t, tc.input.FieldB, actual.FieldB)
+			require.Equal(t, tc.input.FieldC, actual.FieldC)
+			require.Equal(t, tc.input.FieldD, actual.FieldD)
+			require.Equal(t, tc.input.FieldE, actual.FieldE)
+			require.Equal(t, tc.input.FieldF, actual.FieldF)
+			require.Equal(t, tc.input.FieldG, actual.FieldG)
+			require.Equal(t, tc.input.FieldI, actual.FieldI)
+			require.Equal(t, tc.input.FieldJ, actual.FieldJ)
+			require.Equal(t, tc.input.FieldK, actual.FieldK)
+			require.Equal(t, tc.input.FieldH, actual.FieldH)
 		})
+	}
 }
 
-func TestStringMarshal(t *testing.T) {
-	t.Run("not empty", func(t *testing.T) {
-		data := "Hello World"
-		testStringMarshal(t, data, false)
-		testStringMarshal(t, data, true)
-	})
+func randIntSlice[T protoInt](n int, includeZero bool) []T {
+	r := make([]T, n)
+	if n == 0 {
+		return r
+	}
+	for i := range r {
+		r[i] = T(rand.Uint64())
+	}
+	if includeZero {
+		r[0] = 0
+	}
+	return r
+}
 
+func TestStableMarshalRep(t *testing.T) {
 	t.Run("empty", func(t *testing.T) {
-		testStringMarshal(t, "", false)
-	})
-}
-
-func TestBoolMarshal(t *testing.T) {
-	t.Run("true", func(t *testing.T) {
-		testBoolMarshal(t, true, false)
-		testBoolMarshal(t, true, true)
-	})
-
-	t.Run("false", func(t *testing.T) {
-		testBoolMarshal(t, false, false)
-	})
-}
-
-func TestInt32Marshal(t *testing.T) {
-	t.Run("zero", func(t *testing.T) {
-		testInt32Marshal(t, 0, false)
-	})
-
-	t.Run("positive", func(t *testing.T) {
-		testInt32Marshal(t, math.MaxInt32, false)
-		testInt32Marshal(t, math.MaxInt32, true)
-	})
-
-	t.Run("negative", func(t *testing.T) {
-		testInt32Marshal(t, math.MinInt32, false)
-		testInt32Marshal(t, math.MinInt32, true)
-	})
-}
-
-func TestUInt32Marshal(t *testing.T) {
-	t.Run("zero", func(t *testing.T) {
-		testUInt32Marshal(t, 0, false)
-	})
-
-	t.Run("non zero", func(t *testing.T) {
-		testUInt32Marshal(t, math.MaxUint32, false)
-		testUInt32Marshal(t, math.MaxUint32, true)
-	})
-}
-
-func TestInt64Marshal(t *testing.T) {
-	t.Run("zero", func(t *testing.T) {
-		testInt32Marshal(t, 0, false)
-	})
-
-	t.Run("positive", func(t *testing.T) {
-		testInt64Marshal(t, math.MaxInt64, false)
-		testInt64Marshal(t, math.MaxInt64, true)
-	})
-
-	t.Run("negative", func(t *testing.T) {
-		testInt64Marshal(t, math.MinInt64, false)
-		testInt64Marshal(t, math.MinInt64, true)
-	})
-}
-
-func TestUInt64Marshal(t *testing.T) {
-	t.Run("zero", func(t *testing.T) {
-		testUInt64Marshal(t, 0, false)
-	})
-
-	t.Run("non zero", func(t *testing.T) {
-		testUInt64Marshal(t, math.MaxUint64, false)
-		testUInt64Marshal(t, math.MaxUint64, true)
-	})
-}
-
-func TestEnumMarshal(t *testing.T) {
-	testEnumMarshal(t, ENUM_UNKNOWN, false)
-	testEnumMarshal(t, ENUM_POSITIVE, false)
-	testEnumMarshal(t, ENUM_POSITIVE, true)
-	testEnumMarshal(t, ENUM_NEGATIVE, false)
-	testEnumMarshal(t, ENUM_NEGATIVE, true)
-}
-
-func TestRepeatedBytesMarshal(t *testing.T) {
-	t.Run("not empty", func(t *testing.T) {
-		data := [][]byte{[]byte("One"), []byte("Two"), []byte("Three")}
-		testRepeatedBytesMarshal(t, data, false)
-		testRepeatedBytesMarshal(t, data, true)
-	})
-
-	t.Run("empty", func(t *testing.T) {
-		testRepeatedBytesMarshal(t, [][]byte{}, false)
-	})
-
-	t.Run("empty element", func(t *testing.T) {
-		testRepeatedBytesMarshal(t, [][]byte{{1}, {}}, false)
-	})
-
-	t.Run("nil", func(t *testing.T) {
-		testRepeatedBytesMarshal(t, nil, false)
-	})
-}
-
-func TestRepeatedStringMarshal(t *testing.T) {
-	t.Run("not empty", func(t *testing.T) {
-		data := []string{"One", "Two", "Three"}
-		testRepeatedStringMarshal(t, data, false)
-		testRepeatedStringMarshal(t, data, true)
-	})
-
-	t.Run("empty element", func(t *testing.T) {
-		testRepeatedStringMarshal(t, []string{""}, false)
-	})
-
-	t.Run("empty", func(t *testing.T) {
-		testRepeatedStringMarshal(t, []string{}, false)
-	})
-
-	t.Run("nil", func(t *testing.T) {
-		testRepeatedStringMarshal(t, nil, false)
-	})
-}
-
-func TestRepeatedInt32Marshal(t *testing.T) {
-	t.Run("not empty", func(t *testing.T) {
-		data := []int32{-1, 0, 1, 2, 3, 4, 5}
-		testRepeatedInt32Marshal(t, data, false)
-		testRepeatedInt32Marshal(t, data, true)
-	})
-
-	t.Run("empty", func(t *testing.T) {
-		testRepeatedInt32Marshal(t, []int32{}, false)
-	})
-
-	t.Run("nil", func(t *testing.T) {
-		testRepeatedInt32Marshal(t, nil, false)
-	})
-}
-
-func TestRepeatedUInt32Marshal(t *testing.T) {
-	t.Run("not empty", func(t *testing.T) {
-		data := []uint32{0, 1, 2, 3, 4, 5}
-		testRepeatedUInt32Marshal(t, data, false)
-		testRepeatedUInt32Marshal(t, data, true)
-	})
-
-	t.Run("empty", func(t *testing.T) {
-		testRepeatedUInt32Marshal(t, []uint32{}, false)
-	})
-
-	t.Run("nil", func(t *testing.T) {
-		testRepeatedUInt32Marshal(t, nil, false)
-	})
-}
-
-func TestRepeatedInt64Marshal(t *testing.T) {
-	t.Run("not empty", func(t *testing.T) {
-		data := []int64{-1, 0, 1, 2, 3, 4, 5}
-		testRepeatedInt64Marshal(t, data, false)
-		testRepeatedInt64Marshal(t, data, true)
-	})
-
-	t.Run("empty", func(t *testing.T) {
-		testRepeatedInt64Marshal(t, []int64{}, false)
-	})
-
-	t.Run("nil", func(t *testing.T) {
-		testRepeatedInt64Marshal(t, nil, false)
-	})
-}
-
-func TestRepeatedUInt64Marshal(t *testing.T) {
-	t.Run("not empty", func(t *testing.T) {
-		data := []uint64{0, 1, 2, 3, 4, 5}
-		testRepeatedUInt64Marshal(t, data, false)
-		testRepeatedUInt64Marshal(t, data, true)
-	})
-
-	t.Run("empty", func(t *testing.T) {
-		testRepeatedUInt64Marshal(t, []uint64{}, false)
-	})
-
-	t.Run("nil", func(t *testing.T) {
-		testRepeatedUInt64Marshal(t, nil, false)
-	})
-}
-
-func TestRepeatedUInt64MarshalUnpacked(t *testing.T) {
-	t.Run("not empty", func(t *testing.T) {
-		data := []uint64{0, 1, 2, 3, 4, 5}
-		testRepeatedUInt64MarshalUnpacked(t, data, false)
-		testRepeatedUInt64MarshalUnpacked(t, data, true)
-	})
-
-	t.Run("empty", func(t *testing.T) {
-		testRepeatedUInt64MarshalUnpacked(t, []uint64{}, false)
-	})
-
-	t.Run("nil", func(t *testing.T) {
-		testRepeatedUInt64MarshalUnpacked(t, nil, false)
-	})
-}
-
-func TestFixed64Marshal(t *testing.T) {
-	t.Run("zero", func(t *testing.T) {
-		testFixed64Marshal(t, 0, false)
-	})
-
-	t.Run("non zero", func(t *testing.T) {
-		testFixed64Marshal(t, math.MaxUint64, false)
-		testFixed64Marshal(t, math.MaxUint64, true)
-	})
-}
-
-func TestFloat64Marshal(t *testing.T) {
-	t.Run("zero", func(t *testing.T) {
-		testFloat64Marshal(t, 0, false)
-	})
-
-	t.Run("non zero", func(t *testing.T) {
-		f := math.Float64frombits(12345677890)
-
-		testFloat64Marshal(t, f, false)
-		testFloat64Marshal(t, f, true)
-	})
-}
-
-func TestFixed32Marshal(t *testing.T) {
-	t.Run("zero", func(t *testing.T) {
-		testFixed32Marshal(t, 0, false)
-	})
-
-	t.Run("non zero", func(t *testing.T) {
-		testFixed32Marshal(t, math.MaxUint32, false)
-		testFixed32Marshal(t, math.MaxUint32, true)
-	})
-}
-
-func testMarshal(t *testing.T, c stablePrimitives, tr *test.Primitives, wrongField bool) *test.Primitives {
-	var (
-		wire []byte
-		err  error
-	)
-	wire, err = c.stableMarshal(nil, wrongField)
-	require.NoError(t, err)
-
-	wireGen, err := goproto.Marshal(tr)
-	require.NoError(t, err)
-
-	if !wrongField {
-		// we can check equality because single field cannot be unstable marshalled
-		require.Equal(t, wireGen, wire)
-	} else {
-		require.NotEqual(t, wireGen, wire)
+		marshalCases := []struct {
+			name  string
+			input *test.RepPrimitives
+		}{
+			{name: "default", input: &test.RepPrimitives{}},
+			{name: "bytes", input: &test.RepPrimitives{FieldA: [][]byte{}}},
+			{name: "string", input: &test.RepPrimitives{FieldB: []string{}}},
+			{name: "int32", input: &test.RepPrimitives{FieldC: []int32{}}},
+			{name: "uint32", input: &test.RepPrimitives{FieldD: []uint32{}}},
+			{name: "int64", input: &test.RepPrimitives{FieldE: []int64{}}},
+			{name: "uint64", input: &test.RepPrimitives{FieldF: []uint64{}}},
+			{name: "uint64", input: &test.RepPrimitives{FieldFu: []uint64{}}},
 		}
 
-	result := new(test.Primitives)
-	err = goproto.Unmarshal(wire, result)
-	require.NoError(t, err)
+		for _, tc := range marshalCases {
+			require.Zero(t, tc.input.StableSize())
 
-	return result
-}
-
-func testBytesMarshal(t *testing.T, data []byte, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldA: data}
-		transport = test.Primitives{FieldA: data}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Len(t, result.FieldA, len(data))
-		if len(data) > 0 {
-			require.Equal(t, data, result.FieldA)
+			r := tc.input.StableMarshal(nil)
+			require.Empty(t, r)
 		}
-	} else {
-		require.Len(t, result.FieldA, 0)
-	}
-}
-
-func testStringMarshal(t *testing.T, s string, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldB: s}
-		transport = test.Primitives{FieldB: s}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Len(t, result.FieldB, len(s))
-		if len(s) > 0 {
-			require.Equal(t, s, result.FieldB)
-		}
-	} else {
-		require.Len(t, result.FieldB, 0)
-	}
-}
-
-func testBoolMarshal(t *testing.T, b bool, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldC: b}
-		transport = test.Primitives{FieldC: b}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Equal(t, b, result.FieldC)
-	} else {
-		require.False(t, false, result.FieldC)
-	}
-}
-
-func testInt32Marshal(t *testing.T, n int32, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldD: n}
-		transport = test.Primitives{FieldD: n}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Equal(t, n, result.FieldD)
-	} else {
-		require.EqualValues(t, 0, result.FieldD)
-	}
-}
-
-func testUInt32Marshal(t *testing.T, n uint32, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldE: n}
-		transport = test.Primitives{FieldE: n}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Equal(t, n, result.FieldE)
-	} else {
-		require.EqualValues(t, 0, result.FieldE)
-	}
-}
-
-func testInt64Marshal(t *testing.T, n int64, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldF: n}
-		transport = test.Primitives{FieldF: n}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Equal(t, n, result.FieldF)
-	} else {
-		require.EqualValues(t, 0, result.FieldF)
-	}
-}
-
-func testUInt64Marshal(t *testing.T, n uint64, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldG: n}
-		transport = test.Primitives{FieldG: n}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Equal(t, n, result.FieldG)
-	} else {
-		require.EqualValues(t, 0, result.FieldG)
-	}
-}
-
-func testFloat64Marshal(t *testing.T, n float64, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldJ: n}
-		transport = test.Primitives{FieldJ: n}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Equal(t, n, result.FieldJ)
-	} else {
-		require.EqualValues(t, 0, result.FieldJ)
-	}
-}
-
-func testEnumMarshal(t *testing.T, e SomeEnum, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldH: e}
-		transport = test.Primitives{FieldH: test.Primitives_SomeEnum(e)}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.EqualValues(t, custom.FieldH, result.FieldH)
-	} else {
-		require.EqualValues(t, 0, result.FieldH)
-	}
-}
-
-func testRepMarshal(t *testing.T, c stableRepPrimitives, tr *test.RepPrimitives, wrongField bool) *test.RepPrimitives {
-	var (
-		wire []byte
-		err  error
-	)
-	wire, err = c.stableMarshal(nil, wrongField)
-	require.NoError(t, err)
-
-	wireGen, err := goproto.Marshal(tr)
-	require.NoError(t, err)
-
-	if !wrongField {
-		// we can check equality because single field cannot be unstable marshalled
-		require.Equal(t, wireGen, wire)
-	} else {
-		require.NotEqual(t, wireGen, wire)
-	}
-
-	result := new(test.RepPrimitives)
-	err = goproto.Unmarshal(wire, result)
-	require.NoError(t, err)
-
-	return result
-}
-
-func testRepeatedBytesMarshal(t *testing.T, data [][]byte, wrongField bool) {
-	var (
-		custom    = stableRepPrimitives{FieldA: data}
-		transport = test.RepPrimitives{FieldA: data}
-	)
-
-	result := testRepMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Len(t, result.FieldA, len(data))
-		if len(data) > 0 {
-			require.Equal(t, data, result.FieldA)
-		}
-	} else {
-		require.Len(t, result.FieldA, 0)
-	}
-}
-
-func testRepeatedStringMarshal(t *testing.T, s []string, wrongField bool) {
-	var (
-		custom    = stableRepPrimitives{FieldB: s}
-		transport = test.RepPrimitives{FieldB: s}
-	)
-
-	result := testRepMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Len(t, result.FieldB, len(s))
-		if len(s) > 0 {
-			require.Equal(t, s, result.FieldB)
-		}
-	} else {
-		require.Len(t, result.FieldB, 0)
-	}
-}
-
-func testRepeatedInt32Marshal(t *testing.T, n []int32, wrongField bool) {
-	var (
-		custom    = stableRepPrimitives{FieldC: n}
-		transport = test.RepPrimitives{FieldC: n}
-	)
-
-	result := testRepMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Len(t, result.FieldC, len(n))
-		if len(n) > 0 {
-			require.Equal(t, n, result.FieldC)
-		}
-	} else {
-		require.Len(t, result.FieldC, 0)
-	}
-}
-
-func testRepeatedUInt32Marshal(t *testing.T, n []uint32, wrongField bool) {
-	var (
-		custom    = stableRepPrimitives{FieldD: n}
-		transport = test.RepPrimitives{FieldD: n}
-	)
-
-	result := testRepMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Len(t, result.FieldD, len(n))
-		if len(n) > 0 {
-			require.Equal(t, n, result.FieldD)
-		}
-	} else {
-		require.Len(t, result.FieldD, 0)
-	}
-}
-
-func testRepeatedInt64Marshal(t *testing.T, n []int64, wrongField bool) {
-	var (
-		custom    = stableRepPrimitives{FieldE: n}
-		transport = test.RepPrimitives{FieldE: n}
-	)
-
-	result := testRepMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Len(t, result.FieldE, len(n))
-		if len(n) > 0 {
-			require.Equal(t, n, result.FieldE)
-		}
-	} else {
-		require.Len(t, result.FieldE, 0)
-	}
-}
-
-func testRepeatedUInt64Marshal(t *testing.T, n []uint64, wrongField bool) {
-	var (
-		custom    = stableRepPrimitives{FieldF: n}
-		transport = test.RepPrimitives{FieldF: n}
-	)
-
-	result := testRepMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Len(t, result.FieldF, len(n))
-		if len(n) > 0 {
-			require.Equal(t, n, result.FieldF)
-		}
-	} else {
-		require.Len(t, result.FieldF, 0)
-	}
-}
-
-func testRepeatedUInt64MarshalUnpacked(t *testing.T, n []uint64, wrongField bool) {
-	var (
-		custom    = stableRepPrimitives{FieldFu: n}
-		transport = test.RepPrimitives{FieldFu: n}
-	)
-
-	result := testRepMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Len(t, result.FieldFu, len(n))
-		if len(n) > 0 {
-			require.Equal(t, n, result.FieldFu)
-		}
-	} else {
-		require.Len(t, result.FieldFu, 0)
-	}
-}
-
-func testFixed64Marshal(t *testing.T, n uint64, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldI: n}
-		transport = test.Primitives{FieldI: n}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Equal(t, n, result.FieldI)
-	} else {
-		require.EqualValues(t, 0, result.FieldI)
-	}
-}
-
-func testFixed32Marshal(t *testing.T, n uint32, wrongField bool) {
-	var (
-		custom    = stablePrimitives{FieldK: n}
-		transport = test.Primitives{FieldK: n}
-	)
-
-	result := testMarshal(t, custom, &transport, wrongField)
-
-	if !wrongField {
-		require.Equal(t, n, result.FieldK)
-	} else {
-		require.EqualValues(t, 0, result.FieldK)
+	})
+
+	marshalCases := []struct {
+		name  string
+		input *test.RepPrimitives
+	}{
+		{name: "bytes", input: &test.RepPrimitives{FieldA: [][]byte{{1, 2, 3}}}},
+		{name: "string", input: &test.RepPrimitives{FieldB: []string{"123"}}},
+		{name: "int32", input: &test.RepPrimitives{FieldC: randIntSlice[int32](1, true)}},
+		{name: "int32", input: &test.RepPrimitives{FieldC: randIntSlice[int32](2, true)}},
+		{name: "int32", input: &test.RepPrimitives{FieldC: randIntSlice[int32](2, false)}},
+		{name: "uint32", input: &test.RepPrimitives{FieldD: randIntSlice[uint32](1, true)}},
+		{name: "uint32", input: &test.RepPrimitives{FieldD: randIntSlice[uint32](2, true)}},
+		{name: "uint32", input: &test.RepPrimitives{FieldD: randIntSlice[uint32](2, false)}},
+		{name: "int64", input: &test.RepPrimitives{FieldE: randIntSlice[int64](1, true)}},
+		{name: "int64", input: &test.RepPrimitives{FieldE: randIntSlice[int64](2, true)}},
+		{name: "int64", input: &test.RepPrimitives{FieldE: randIntSlice[int64](2, false)}},
+		{name: "uint64", input: &test.RepPrimitives{FieldF: randIntSlice[uint64](1, true)}},
+		{name: "uint64", input: &test.RepPrimitives{FieldF: randIntSlice[uint64](2, true)}},
+		{name: "uint64", input: &test.RepPrimitives{FieldF: randIntSlice[uint64](2, false)}},
+		{name: "uint64", input: &test.RepPrimitives{FieldFu: randIntSlice[uint64](1, true)}},
+		{name: "uint64", input: &test.RepPrimitives{FieldFu: randIntSlice[uint64](2, true)}},
+		{name: "uint64", input: &test.RepPrimitives{FieldFu: randIntSlice[uint64](2, false)}},
+	}
+	for _, tc := range marshalCases {
+		t.Run(tc.name, func(t *testing.T) {
+			r := tc.input.StableMarshal(nil)
+			require.Equal(t, len(r), tc.input.StableSize())
+			require.NotEmpty(t, r)
+
+			var actual test.RepPrimitives
+			require.NoError(t, goproto.Unmarshal(r, &actual))
+
+			// Compare each field directly, because proto-generated code has private fields.
+			require.Equal(t, tc.input.FieldA, actual.FieldA)
+			require.Equal(t, tc.input.FieldB, actual.FieldB)
+			require.Equal(t, tc.input.FieldC, actual.FieldC)
+			require.Equal(t, tc.input.FieldD, actual.FieldD)
+			require.Equal(t, tc.input.FieldE, actual.FieldE)
+			require.Equal(t, tc.input.FieldF, actual.FieldF)
+			require.Equal(t, tc.input.FieldFu, actual.FieldFu)
+		})
 	}
 }