cmd/go: make all script tests parallel

Move the last non-parallel test to verylongtest, and then check that all
go command invocations in the tests occur in a parallel context. Note
that because TestBuildmodePie starts in a subtest, that the check for
invocations in a parallel context wouldn't catch that the parent test
didn't call t.Parallel.

For #78152

Change-Id: Ie053e56af8efaaea6de9ce6fccbd20f76a6a6964
Reviewed-on: https://go-review.googlesource.com/c/go/+/755140
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Michael Matloob <matloob@google.com>
Auto-Submit: Michael Matloob <matloob@golang.org>

src/cmd/go/chdir_test.go

@@ -12,6 +12,8 @@ import (
 )
 
 func TestChdir(t *testing.T) {
+	t.Parallel()
+
 	// We want -C to apply to every go subcommand.
 	// Test that every command either has a -C flag registered
 	// or has CustomFlags set. In the latter case, the command

src/cmd/go/go_test.go

@@ -487,11 +487,12 @@ func (tg *testgoData) goTool() string {
 // returning exit status.
 func (tg *testgoData) doRun(args []string) error {
 	tg.t.Helper()
-	if tg.inParallel {
-		for _, arg := range args {
-			if strings.HasPrefix(arg, "testdata") || strings.HasPrefix(arg, "./testdata") {
-				tg.t.Fatal("internal testsuite error: parallel run using testdata")
-			}
+	if !tg.inParallel {
+		tg.t.Fatal("all tests using testgoData must run in parallel")
+	}
+	for _, arg := range args {
+		if strings.HasPrefix(arg, "testdata") || strings.HasPrefix(arg, "./testdata") {
+			tg.t.Fatal("internal testsuite error: parallel run using testdata")
 		}
 	}
 
@@ -1948,6 +1949,7 @@ func TestNeedVersion(t *testing.T) {
 
 func TestBuildmodePIE(t *testing.T) {
 	tooSlow(t, "links binaries")
+	t.Parallel()
 
 	if !platform.BuildModeSupported(runtime.Compiler, "pie", runtime.GOOS, runtime.GOARCH) {
 		t.Skipf("skipping test because buildmode=pie is not supported on %s/%s", runtime.GOOS, runtime.GOARCH)
@@ -1970,6 +1972,7 @@ func TestWindowsDefaultBuildmodIsPIE(t *testing.T) {
 		t.Skip("skipping windows only test")
 	}
 	tooSlow(t, "links binaries")
+	t.Parallel()
 
 	t.Run("non-cgo", func(t *testing.T) {
 		testBuildmodePIE(t, false, false)
@@ -2651,24 +2654,3 @@ func TestCoverpkgTestOnly(t *testing.T) {
 	tg.grepStderrNot("no packages being tested depend on matches", "bad match message")
 	tg.grepStdout("coverage: 100", "no coverage")
 }
-
-// Regression test for golang.org/issue/34499: version command should not crash
-// when executed in a deleted directory on Linux.
-func TestExecInDeletedDir(t *testing.T) {
-	switch runtime.GOOS {
-	case "windows", "plan9",
-		"aix",                // Fails with "device busy".
-		"solaris", "illumos": // Fails with "invalid argument".
-		t.Skipf("%v does not support removing the current working directory", runtime.GOOS)
-	}
-	tg := testgo(t)
-	defer tg.cleanup()
-
-	tg.makeTempdir()
-	t.Chdir(tg.tempdir)
-
-	tg.check(os.Remove(tg.tempdir))
-
-	// `go version` should not fail
-	tg.run("version")
-}

src/cmd/go/internal/verylongtest/go_test.go

@@ -0,0 +1,43 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package verylongtest
+
+import (
+	"bytes"
+	"internal/testenv"
+	"os"
+	"os/exec"
+	"runtime"
+	"testing"
+)
+
+// Regression test for golang.org/issue/34499: version command should not crash
+// when executed in a deleted directory on Linux.
+func TestExecInDeletedDir(t *testing.T) {
+	switch runtime.GOOS {
+	case "windows", "plan9",
+		"aix",                // Fails with "device busy".
+		"solaris", "illumos": // Fails with "invalid argument".
+		t.Skipf("%v does not support removing the current working directory", runtime.GOOS)
+	}
+	gotool := testenv.GoToolPath(t)
+
+	tmpdir := t.TempDir()
+	t.Chdir(tmpdir)
+
+	if err := os.Remove(tmpdir); err != nil {
+		t.Fatal(err)
+	}
+
+	// `go version` should not fail
+	var stdout, stderr bytes.Buffer
+	cmd := exec.Command(gotool, "version")
+	cmd.Env = append(os.Environ(), "GO111MODULE=off") // This behavior doesn't apply with GO111MODULE != off because we need to know the module to check the version.
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	if err := cmd.Run(); err != nil {
+		t.Fatalf("running go version: %v\n[stdout]: %s\n[stderr]: %s", err, stdout.Bytes(), stderr.Bytes())
+	}
+}

src/cmd/go/script_test.go

@@ -38,6 +38,8 @@ var testSum = flag.String("testsum", "", `may be tidy, listm, or listall. If set
 
 // TestScript runs the tests in testdata/script/*.txt.
 func TestScript(t *testing.T) {
+	t.Parallel()
+
 	testenv.MustHaveGoBuild(t)
 	testenv.SkipIfShortAndSlow(t)
 
@@ -99,6 +101,7 @@ func TestScript(t *testing.T) {
 	}
 
 	t.Run("README", func(t *testing.T) {
+		t.Parallel()
 		checkScriptReadme(t, engine, env)
 	})
 

src/cmd/go/terminal_test.go

@@ -16,6 +16,8 @@ import (
 )
 
 func TestTerminalPassthrough(t *testing.T) {
+	t.Parallel()
+
 	// Check that if 'go test' is run with a terminal connected to stdin/stdout,
 	// then the go command passes that terminal down to the test binary
 	// invocation (rather than, e.g., putting a pipe in the way).
@@ -27,6 +29,7 @@ func TestTerminalPassthrough(t *testing.T) {
 	// terminal, the test can correctly detect that. (cmd/go doesn't guarantee
 	// that it won't add a terminal in the middle, but that would be pretty weird.)
 	t.Run("pipe", func(t *testing.T) {
+		t.Parallel()
 		r, w, err := os.Pipe()
 		if err != nil {
 			t.Fatalf("pipe failed: %s", err)
@@ -44,6 +47,7 @@ func TestTerminalPassthrough(t *testing.T) {
 
 	// Now test with a read PTY.
 	t.Run("pty", func(t *testing.T) {
+		t.Parallel()
 		r, processTTY, err := testpty.Open()
 		if errors.Is(err, testpty.ErrNotSupported) {
 			t.Skipf("%s", err)