test(cmd): cover registry client stderr routing via OCI pull

Exercise helm template and helm show against an in-process OCI registry
(repotest.NewOCIServer) and assert Pulled:/Digest: status lines appear
on stderr only, keeping stdout free of registry noise.

Signed-off-by: amarkdotdev <amarkdotdev@users.noreply.github.com>

pkg/cmd/registry_output_test.go

@@ -0,0 +1,116 @@
+/*
+Copyright The Helm 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 cmd
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"helm.sh/helm/v4/pkg/action"
+	"helm.sh/helm/v4/pkg/chart/common"
+	kubefake "helm.sh/helm/v4/pkg/kube/fake"
+	"helm.sh/helm/v4/pkg/repo/v1/repotest"
+)
+
+func TestTemplateOCIRegistryMessagesNotOnStdout(t *testing.T) {
+	defer resetEnv()()
+
+	stdout, stderr := runOCIChartCommand(t, func(ref, registryConfig, contentCache string) []string {
+		return []string{
+			"template", "release-name", ref,
+			"--version", "0.1.0",
+			"--plain-http",
+			"--registry-config", registryConfig,
+			"--content-cache", contentCache,
+		}
+	})
+
+	require.NotEmpty(t, stdout)
+	require.NotContains(t, stdout, "Pulled:")
+	require.NotContains(t, stdout, "Digest:")
+	require.Contains(t, stderr, "Pulled:")
+	require.Contains(t, stderr, "Digest:")
+}
+
+func TestShowOCIRegistryMessagesNotOnStdout(t *testing.T) {
+	defer resetEnv()()
+
+	stdout, stderr := runOCIChartCommand(t, func(ref, registryConfig, contentCache string) []string {
+		return []string{
+			"show", "chart", ref,
+			"--version", "0.1.0",
+			"--plain-http",
+			"--registry-config", registryConfig,
+			"--content-cache", contentCache,
+		}
+	})
+
+	require.NotEmpty(t, stdout)
+	require.Contains(t, stdout, "name: oci-dependent-chart")
+	require.NotContains(t, stdout, "Pulled:")
+	require.NotContains(t, stdout, "Digest:")
+	require.Contains(t, stderr, "Pulled:")
+	require.Contains(t, stderr, "Digest:")
+}
+
+func TestAddRegistryClientUsesProvidedWriter(t *testing.T) {
+	writer := &bytes.Buffer{}
+	client := action.NewShow(action.ShowChart, &action.Configuration{})
+
+	require.NoError(t, addRegistryClient(writer, client))
+}
+
+func runOCIChartCommand(t *testing.T, argsFn func(ref, registryConfig, contentCache string) []string) (string, string) {
+	t.Helper()
+
+	srv := repotest.NewTempServer(
+		t,
+		repotest.WithChartSourceGlob("testdata/testcharts/*.tgz*"),
+	)
+	t.Cleanup(func() { srv.Stop() })
+
+	ociSrv, err := repotest.NewOCIServer(t, srv.Root())
+	require.NoError(t, err)
+	ociSrv.Run(t)
+
+	ref := fmt.Sprintf("oci://%s/u/ocitestuser/oci-dependent-chart", ociSrv.RegistryURL)
+	registryConfig := filepath.Join(srv.Root(), "config.json")
+	contentCache := t.TempDir()
+	args := argsFn(ref, registryConfig, contentCache)
+
+	stdout := &bytes.Buffer{}
+	stderr := &bytes.Buffer{}
+	actionConfig := &action.Configuration{
+		Releases:     storageFixture(),
+		KubeClient:   &kubefake.PrintingKubeClient{Out: io.Discard},
+		Capabilities: common.DefaultCapabilities,
+	}
+
+	root, err := newRootCmdWithConfig(actionConfig, stdout, args, SetupLogging)
+	require.NoError(t, err)
+	root.SetOut(stdout)
+	root.SetErr(stderr)
+	root.SetArgs(args)
+
+	require.NoError(t, root.Execute(), "stdout:\n%s\nstderr:\n%s", stdout.String(), stderr.String())
+	return stdout.String(), stderr.String()
+}