🌱 Implement a smoke test for clusterctl plugins

Author: dmvolod

cmd/clusterctl/cmd/plugin_test.go

@@ -0,0 +1,105 @@
+/*
+Copyright 2025 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 cmd
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"testing"
+
+	"github.com/Masterminds/goutils"
+	. "github.com/onsi/gomega"
+)
+
+var baseArgs = []string{"clusterctl", "foo"}
+
+const (
+	forkEnvVar          = "FORK"
+	pluginCommandEnvVar = "PLUGIN_COMMAND"
+)
+
+func Test_plugin(t *testing.T) {
+	tt := []struct {
+		name     string
+		command  string
+		expected string
+	}{
+		{
+			name:     "base plugin command test",
+			expected: "I am a plugin named clusterctl-foo",
+		},
+		{
+			name:     "plugin version command test",
+			command:  "version",
+			expected: "1.0.0",
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			g := NewWithT(t)
+			stdout, _, err := runForkTest("TestExecutePlugin", fmt.Sprintf("%s=%s", pluginCommandEnvVar, tc.command))
+			g.Expect(err).NotTo(HaveOccurred())
+			g.Expect(stdout).To(ContainSubstring(tc.expected))
+		})
+	}
+}
+
+func TestExecutePlugin(t *testing.T) {
+	g := NewWithT(t)
+	if goutils.DefaultString(os.Getenv(forkEnvVar), "false") == strconv.FormatBool(false) {
+		t.Skip("FORK environment variable isn't set. Skipping test")
+	}
+
+	tmpDir := t.TempDir()
+	path := filepath.Join(tmpDir, "clusterctl-foo")
+	g.Expect(os.WriteFile(path, []byte(pluginCode), 0755)).To(Succeed()) //nolint:gosec
+	g.Expect(os.Setenv("PATH", fmt.Sprintf("%s:%s", os.Getenv("PATH"), tmpDir))).ToNot(HaveOccurred())
+
+	os.Args = append(baseArgs, os.Getenv(pluginCommandEnvVar))
+	Execute()
+}
+
+const pluginCode = `
+#!/bin/bash
+
+# optional argument handling
+if [[ "$1" == "version" ]]
+then
+echo "1.0.0"
+exit 0
+fi
+
+echo "I am a plugin named clusterctl-foo"
+`
+
+func runForkTest(testName string, option string) (string, string, error) {
+	cmd := exec.Command(os.Args[0], fmt.Sprintf("-test.run=%v", testName)) //nolint:gosec
+	cmd.Env = append(os.Environ(), fmt.Sprintf("%s=%v", forkEnvVar, true), option)
+
+	var stdoutB, stderrB bytes.Buffer
+	cmd.Stdout = &stdoutB
+	cmd.Stderr = &stderrB
+
+	err := cmd.Run()
+
+	return stdoutB.String(), stderrB.String(), err
+}

cmd/clusterctl/cmd/root.go

@@ -218,7 +218,7 @@ func handlePlugins() {
 			case "help", cobra.ShellCompRequestCmd, cobra.ShellCompNoDescRequestCmd:
 				// Don't search for a plugin
 			default:
-				if err := handlePluginCommand(pluginHandler, cmdPathPieces, 0); err != nil {
+				if err = handlePluginCommand(pluginHandler, cmdPathPieces, 0); err != nil {
 					fmt.Fprintf(os.Stderr, "Error: %v\n", err)
 					os.Exit(1)
 				}