[#108] rpc/message: Add compatibility tests for marshaling

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

rpc/message/test/message.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/rpc/message"
+	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/util/proto/encoding"
 	"github.com/stretchr/testify/require"
 )
 
@@ -68,6 +69,64 @@ func TestRPCMessage(t *testing.T, msgGens ...func(empty bool) message.Message) {
 					require.Equal(t, bm, bm2)
 				})
 			}
+			t.Run("compatibility", func(t *testing.T) {
+				testCompatibility(t, msgGen)
+			})
 		})
 	}
 }
+
+func testCompatibility(t *testing.T, msgGen func(empty bool) message.Message) {
+	compareBinary := func(t *testing.T, msg message.Message) {
+		am, ok := msg.(binaryMessage)
+		if !ok {
+			t.Skip()
+		}
+
+		a := am.StableMarshal(nil)
+		b := msg.ToGRPCMessage().(encoding.ProtoMarshaler).MarshalProtobuf(nil)
+		if len(a) == 0 {
+			require.Empty(t, b)
+		} else {
+			require.Equal(t, a, b)
+		}
+	}
+	compareJSON := func(t *testing.T, msg message.Message) {
+		am, ok := msg.(jsonMessage)
+		if !ok {
+			t.Skip()
+		}
+
+		a, err := am.MarshalJSON()
+		require.NoError(t, err)
+
+		b, err := json.Marshal(msg.ToGRPCMessage())
+		require.NoError(t, err)
+
+		require.JSONEq(t, string(a), string(b))
+		if len(a) == 0 {
+			require.Empty(t, b)
+		} else {
+			require.Equal(t, a, b)
+		}
+	}
+	t.Run("empty", func(t *testing.T) {
+		t.Skip()
+		msg := msgGen(true)
+		t.Run(fmt.Sprintf("Binary_%T", msg), func(t *testing.T) {
+			compareBinary(t, msg)
+		})
+		t.Run(fmt.Sprintf("JSON_%T", msg), func(t *testing.T) {
+			compareJSON(t, msg)
+		})
+	})
+	t.Run("not empty", func(t *testing.T) {
+		msg := msgGen(false)
+		t.Run(fmt.Sprintf("Binary_%T", msg), func(t *testing.T) {
+			compareBinary(t, msg)
+		})
+		t.Run(fmt.Sprintf("JSON_%T", msg), func(t *testing.T) {
+			compareJSON(t, msg)
+		})
+	})
+}