openapi: add spec roundtrip test

pkg/generated/openapi/BUILD

 package(default_visibility = ["//visibility:public"])
 
 load("//build:code_generation.bzl", "gen_openapi", "openapi_deps")
-load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
 
 gen_openapi(
     outs = ["zz_generated.openapi.go"],
@@ -30,3 +30,13 @@ filegroup(
     srcs = [":package-srcs"],
     tags = ["automanaged"],
 )
+
+go_test(
+    name = "go_default_test",
+    srcs = ["openapi_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//staging/src/k8s.io/apimachinery/pkg/util/diff:go_default_library",
+        "//vendor/github.com/go-openapi/spec:go_default_library",
+    ],
+)

pkg/generated/openapi/openapi_test.go

+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package openapi
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+
+	"github.com/go-openapi/spec"
+
+	"k8s.io/apimachinery/pkg/util/diff"
+)
+
+func TestOpenAPIRoundtrip(t *testing.T) {
+	dummyRef := func(name string) spec.Ref { return spec.MustCreateRef("#/definitions/dummy") }
+	for name, value := range GetOpenAPIDefinitions(dummyRef) {
+		t.Run(name, func(t *testing.T) {
+			data, err := json.Marshal(value.Schema)
+			if err != nil {
+				t.Error(err)
+				return
+			}
+
+			roundTripped := spec.Schema{}
+			if err := json.Unmarshal(data, &roundTripped); err != nil {
+				t.Error(err)
+				return
+			}
+
+			if !reflect.DeepEqual(value.Schema, roundTripped) {
+				t.Errorf("unexpected diff (a=expected,b=roundtripped):\n%s", diff.ObjectReflectDiff(value.Schema, roundTripped))
+				return
+			}
+		})
+	}
+}