feat(internal/command): add RequireCommand test helper (#2978)

A RequireCommand test helper function is added to skip tests when
required external commands are not installed. This function is exported
from the internal/command package and can be used across test files.

The helper replaces the previous requireCommand, requireProtoc, and
requireCargo functions that were defined in internal/sidekick/sidekick.

Author: julieqiu

internal/command/testhelpers.go

@@ -0,0 +1,31 @@
+// Copyright 2025 Google LLC
+//
+// 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
+//
+//     https://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 command
+
+import (
+	"os/exec"
+	"testing"
+)
+
+// RequireCommand skips the test if the specified command is not found in PATH.
+// Use this to skip tests that depend on external tools like protoc, cargo, or
+// taplo, so that `go test ./...` will always pass on a fresh clone of the
+// repo.
+func RequireCommand(t *testing.T, command string) {
+	t.Helper()
+	if _, err := exec.LookPath(command); err != nil {
+		t.Skipf("skipping test because %s is not installed", command)
+	}
+}

internal/sidekick/sidekick/rust_bump_versions_test.go

@@ -17,10 +17,12 @@ package sidekick
 import (
 	"testing"
 
+	cmdtest "github.com/googleapis/librarian/internal/command"
 	"github.com/googleapis/librarian/internal/sidekick/config"
 )
 
 func TestRustBumpVersions(t *testing.T) {
+	cmdtest.RequireCommand(t, "taplo")
 	config := &config.Config{
 		Release: &config.Release{
 			Preinstalled: map[string]string{

internal/sidekick/sidekick/sidekick_rust_prost_convert_test.go

@@ -17,10 +17,12 @@ package sidekick
 import (
 	"path"
 	"testing"
+
+	cmdtest "github.com/googleapis/librarian/internal/command"
 )
 
 func TestRustProstConvert(t *testing.T) {
-	requireProtoc(t)
+	cmdtest.RequireCommand(t, "protoc")
 	outDir := t.TempDir()
 
 	type TestConfig struct {

internal/sidekick/sidekick/sidekick_rust_prost_test.go

@@ -18,11 +18,13 @@ import (
 	"os"
 	"path"
 	"testing"
+
+	cmdtest "github.com/googleapis/librarian/internal/command"
 )
 
 func TestRustProstFromProtobuf(t *testing.T) {
-	requireCargo(t)
-	requireProtoc(t)
+	cmdtest.RequireCommand(t, "cargo")
+	cmdtest.RequireCommand(t, "protoc")
 	outDir := t.TempDir()
 	svcConfig := path.Join(testdataDir, "googleapis/google/type/type.yaml")
 	specificationSource := path.Join(testdataDir, "googleapis/google/type")

internal/sidekick/sidekick/sidekick_sample_test.go

@@ -18,10 +18,12 @@ import (
 	"os"
 	"path"
 	"testing"
+
+	cmdtest "github.com/googleapis/librarian/internal/command"
 )
 
 func TestSampleFromProtobuf(t *testing.T) {
-	requireProtoc(t)
+	cmdtest.RequireCommand(t, "protoc")
 	outDir := t.TempDir()
 	svcConfig := path.Join(testdataDir, "googleapis/google/type/type.yaml")
 	specificationSource := path.Join(testdataDir, "googleapis/google/type")

internal/sidekick/sidekick/sidekick_test.go

@@ -16,9 +16,7 @@ package sidekick
 
 import (
 	"fmt"
-	"os/exec"
 	"path/filepath"
-	"testing"
 )
 
 const (
@@ -31,18 +29,3 @@ var (
 	outputDir           = fmt.Sprintf("%s/test-only", testdataDir)
 	specificationSource = fmt.Sprintf("%s/openapi/secretmanager_openapi_v1.json", testdataDir)
 )
-
-func requireCommand(t *testing.T, command string) {
-	t.Helper()
-	if _, err := exec.LookPath(command); err != nil {
-		t.Skipf("skipping test because %s is not installed", command)
-	}
-}
-
-func requireProtoc(t *testing.T) {
-	requireCommand(t, "protoc")
-}
-
-func requireCargo(t *testing.T) {
-	requireCommand(t, "cargo")
-}