Add builtin label transformer.

plugin/builtin/labeltransformer/LabelTransformer_test.go

@@ -0,0 +1,55 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package main_test
+
+import (
+	"testing"
+
+	"sigs.k8s.io/kustomize/pkg/kusttest"
+	"sigs.k8s.io/kustomize/plugin"
+)
+
+func TestLabelTransformer(t *testing.T) {
+	tc := plugin.NewEnvForTest(t).Set()
+	defer tc.Reset()
+
+	tc.BuildGoPlugin(
+		"builtin", "", "LabelTransformer")
+
+	th := kusttest_test.NewKustTestPluginHarness(t, "/app")
+
+	rm := th.LoadAndRunTransformer(`
+apiVersion: builtin
+kind: LabelTransformer
+metadata:
+  name: notImportantHere
+labels:
+  app: myApp
+  env: production
+fieldSpecs:
+  - path: metadata/labels
+    create: true
+`, `
+apiVersion: v1
+kind: Service
+metadata:
+  name: myService
+spec:
+  ports:
+  - port: 7002
+`)
+
+	th.AssertActualEqualsExpected(rm, `
+apiVersion: v1
+kind: Service
+metadata:
+  labels:
+    app: myApp
+    env: production
+  name: myService
+spec:
+  ports:
+  - port: 7002
+`)
+}