From c1ff7592fa90e6b8cfb4beb8b7c3b10acb4abed3 Mon Sep 17 00:00:00 2001
From: Clayton Coleman <ccoleman@redhat.com>
Date: Sat, 17 Jun 2017 14:32:35 -0400
Subject: [PATCH] Add test for stable encoding

---
 .../apimachinery/pkg/api/testing/roundtrip.go  | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/staging/src/k8s.io/apimachinery/pkg/api/testing/roundtrip.go b/staging/src/k8s.io/apimachinery/pkg/api/testing/roundtrip.go
index 8e665d86f89..b3070599156 100644
--- a/staging/src/k8s.io/apimachinery/pkg/api/testing/roundtrip.go
+++ b/staging/src/k8s.io/apimachinery/pkg/api/testing/roundtrip.go
@@ -17,6 +17,7 @@ limitations under the License.
 package testing
 
 import (
+	"bytes"
 	"encoding/hex"
 	"fmt"
 	"reflect"
@@ -282,6 +283,23 @@ func roundTrip(t *testing.T, scheme *runtime.Scheme, codec runtime.Codec, object
 		return
 	}
 
+	// encode (serialize) a second time to verify that it was not varying
+	secondData, err := runtime.Encode(codec, object)
+	if err != nil {
+		if runtime.IsNotRegisteredError(err) {
+			t.Logf("%v: not registered: %v (%s)", name, err, printer.Sprintf("%#v", object))
+		} else {
+			t.Errorf("%v: %v (%s)", name, err, printer.Sprintf("%#v", object))
+		}
+		return
+	}
+
+	// serialization to the wire must be stable to ensure that we don't write twice to the DB
+	// when the object hasn't changed.
+	if !bytes.Equal(data, secondData) {
+		t.Errorf("%v: serialization is not stable: %s", name, printer.Sprintf("%#v", object))
+	}
+
 	// decode (deserialize) the encoded data back into an object
 	obj2, err := runtime.Decode(codec, data)
 	if err != nil {