Gather and use some of the kyaml constants.

kyaml/yaml/kfns_test.go

@@ -16,7 +16,7 @@ data:
   enableRisky: "false"
 `
 
-func TestSetLabel(t *testing.T) {
+func TestSetLabel1(t *testing.T) {
 	rn := MustParse(input)
 	_, err := rn.Pipe(SetLabel("foo", "bar"))
 	if err != nil {
@@ -39,6 +39,31 @@ data:
 	}
 }
 
+func TestSetLabel2(t *testing.T) {
+	rn := MustParse(`apiVersion: v1
+kind: ConfigMap
+data:
+  altGreeting: "Good Morning!"
+`)
+	_, err := rn.Pipe(SetLabel("foo", "bar"))
+	if err != nil {
+		t.Fatalf("unexpected error %v", err)
+	}
+	output := rn.MustString()
+
+	expected := `apiVersion: v1
+kind: ConfigMap
+data:
+  altGreeting: "Good Morning!"
+metadata:
+  labels:
+    foo: 'bar'
+`
+	if output != expected {
+		t.Fatalf("expected \n%s\nbut got \n%s\n", expected, output)
+	}
+}
+
 func TestAnnotation(t *testing.T) {
 	rn := MustParse(input)
 	_, err := rn.Pipe(SetAnnotation("foo", "bar"))