1 files changed, 40 insertions, 0 deletions
diff --git a/internal/encoding/tag/tag_test.go b/internal/encoding/tag/tag_test.go
new file mode 100644
index 00000000..9f22521d
--- /dev/null
+++ b/internal/encoding/tag/tag_test.go
@@ -0,0 +1,40 @@
+// Copyright 2018 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.
+
+package tag_test
+
+import (
+	"reflect"
+	"testing"
+
+	"google.golang.org/protobuf/internal/encoding/tag"
+	fdesc "google.golang.org/protobuf/internal/filedesc"
+	"google.golang.org/protobuf/proto"
+	pdesc "google.golang.org/protobuf/reflect/protodesc"
+	pref "google.golang.org/protobuf/reflect/protoreflect"
+)
+
+func Test(t *testing.T) {
+	fd := new(fdesc.Field)
+	fd.L0.ParentFile = fdesc.SurrogateProto3
+	fd.L0.FullName = "foo_field"
+	fd.L1.Number = 1337
+	fd.L1.Cardinality = pref.Repeated
+	fd.L1.Kind = pref.BytesKind
+	fd.L1.Default = fdesc.DefaultValue(pref.ValueOf([]byte("hello, \xde\xad\xbe\xef\n")), nil)
+
+	// Marshal test.
+	gotTag := tag.Marshal(fd, "")
+	wantTag := `bytes,1337,rep,name=foo_field,json=fooField,proto3,def=hello, \336\255\276\357\n`
+	if gotTag != wantTag {
+		t.Errorf("Marshal() = `%v`, want `%v`", gotTag, wantTag)
+	}
+
+	// Unmarshal test.
+	gotFD := tag.Unmarshal(wantTag, reflect.TypeOf([]byte{}), nil)
+	wantFD := fd
+	if !proto.Equal(pdesc.ToFieldDescriptorProto(gotFD), pdesc.ToFieldDescriptorProto(wantFD)) {
+		t.Errorf("Umarshal() mismatch:\ngot  %v\nwant %v", gotFD, wantFD)
+	}
+}