src/internal/testenv/testenv.go - go - Git at Google

 // Copyright 2015 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 testenv provides information about what functionality
 // is available in different testing environments run by the Go team.
 //
 // It is an internal package because these details are specific
 // to the Go team's test setup (on build.golang.org) and not
 // fundamental to tests in general.
 package testenv

 import (
 	"bytes"
 	"errors"
 	"flag"
 	"fmt"
 	"internal/cfg"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
 	"strconv"
 	"strings"
 	"sync"
 	"testing"
 	"time"
 )

 // Builder reports the name of the builder running this test
 // (for example, "linux-amd64" or "windows-386-gce").
 // If the test is not running on the build infrastructure,
 // Builder returns the empty string.
 func Builder() string {
 	return os.Getenv("GO_BUILDER_NAME")
 }

 // HasGoBuild reports whether the current system can build programs with “go build”
 // and then run them with os.StartProcess or exec.Command.
 func HasGoBuild() bool {
 	if os.Getenv("GO_GCFLAGS") != "" {
 		// It's too much work to require every caller of the go command
 		// to pass along "-gcflags="+os.Getenv("GO_GCFLAGS").
 		// For now, if $GO_GCFLAGS is set, report that we simply can't
 		// run go build.
 		return false
 	}
 	switch runtime.GOOS {
 	case "android", "js", "ios":
 		return false
 	}
 	return true
 }

 // MustHaveGoBuild checks that the current system can build programs with “go build”
 // and then run them with os.StartProcess or exec.Command.
 // If not, MustHaveGoBuild calls t.Skip with an explanation.
 func MustHaveGoBuild(t testing.TB) {
 	if os.Getenv("GO_GCFLAGS") != "" {
 		t.Skipf("skipping test: 'go build' not compatible with setting $GO_GCFLAGS")
 	}
 	if !HasGoBuild() {
 		t.Skipf("skipping test: 'go build' not available on %s/%s", runtime.GOOS, runtime.GOARCH)
 	}
 }

 // HasGoRun reports whether the current system can run programs with “go run.”
 func HasGoRun() bool {
 	// For now, having go run and having go build are the same.
 	return HasGoBuild()
 }

 // MustHaveGoRun checks that the current system can run programs with “go run.”
 // If not, MustHaveGoRun calls t.Skip with an explanation.
 func MustHaveGoRun(t testing.TB) {
 	if !HasGoRun() {
 		t.Skipf("skipping test: 'go run' not available on %s/%s", runtime.GOOS, runtime.GOARCH)
 	}
 }

 // GoToolPath reports the path to the Go tool.
 // It is a convenience wrapper around GoTool.
 // If the tool is unavailable GoToolPath calls t.Skip.
 // If the tool should be available and isn't, GoToolPath calls t.Fatal.
 func GoToolPath(t testing.TB) string {
 	MustHaveGoBuild(t)
 	path, err := GoTool()
 	if err != nil {
 		t.Fatal(err)
 	}
 	// Add all environment variables that affect the Go command to test metadata.
 	// Cached test results will be invalidate when these variables change.
 	// See golang.org/issue/32285.
 	for _, envVar := range strings.Fields(cfg.KnownEnv) {
 		os.Getenv(envVar)
 	}
 	return path
 }

 var (
 	gorootOnce sync.Once
 	gorootPath string
 	gorootErr  error
 )

 func findGOROOT() (string, error) {
 	gorootOnce.Do(func() {
 		gorootPath = runtime.GOROOT()
 		if gorootPath != "" {
 			// If runtime.GOROOT() is non-empty, assume that it is valid.
 			//
 			// (It might not be: for example, the user may have explicitly set GOROOT
 			// to the wrong directory, or explicitly set GOROOT_FINAL but not GOROOT
 			// and hasn't moved the tree to GOROOT_FINAL yet. But those cases are
 			// rare, and if that happens the user can fix what they broke.)
 			return
 		}

 		// runtime.GOROOT doesn't know where GOROOT is (perhaps because the test
 		// binary was built with -trimpath, or perhaps because GOROOT_FINAL was set
 		// without GOROOT and the tree hasn't been moved there yet).
 		//
 		// Since this is internal/testenv, we can cheat and assume that the caller
 		// is a test of some package in a subdirectory of GOROOT/src. ('go test'
 		// runs the test in the directory containing the packaged under test.) That
 		// means that if we start walking up the tree, we should eventually find
 		// GOROOT/src/go.mod, and we can report the parent directory of that.

 		cwd, err := os.Getwd()
 		if err != nil {
 			gorootErr = fmt.Errorf("finding GOROOT: %w", err)
 			return
 		}

 		dir := cwd
 		for {
 			parent := filepath.Dir(dir)
 			if parent == dir {
 				// dir is either "." or only a volume name.
 				gorootErr = fmt.Errorf("failed to locate GOROOT/src in any parent directory")
 				return
 			}

 			if base := filepath.Base(dir); base != "src" {
 				dir = parent
 				continue // dir cannot be GOROOT/src if it doesn't end in "src".
 			}

 			b, err := os.ReadFile(filepath.Join(dir, "go.mod"))
 			if err != nil {
 				if os.IsNotExist(err) {
 					dir = parent
 					continue
 				}
 				gorootErr = fmt.Errorf("finding GOROOT: %w", err)
 				return
 			}
 			goMod := string(b)

 			for goMod != "" {
 				var line string
 				line, goMod, _ = strings.Cut(goMod, "\n")
 				fields := strings.Fields(line)
 				if len(fields) >= 2 && fields[0] == "module" && fields[1] == "std" {
 					// Found "module std", which is the module declaration in GOROOT/src!
 					gorootPath = parent
 					return
 				}
 			}
 		}
 	})

 	return gorootPath, gorootErr
 }

 // GOROOT reports the path to the directory containing the root of the Go
 // project source tree. This is normally equivalent to runtime.GOROOT, but
 // works even if the test binary was built with -trimpath.
 //
 // If GOROOT cannot be found, GOROOT skips t if t is non-nil,
 // or panics otherwise.
 func GOROOT(t testing.TB) string {
 	path, err := findGOROOT()
 	if err != nil {
 		if t == nil {
 			panic(err)
 		}
 		t.Helper()
 		t.Skip(err)
 	}
 	return path
 }

 // GoTool reports the path to the Go tool.
 func GoTool() (string, error) {
 	if !HasGoBuild() {
 		return "", errors.New("platform cannot run go tool")
 	}
 	var exeSuffix string
 	if runtime.GOOS == "windows" {
 		exeSuffix = ".exe"
 	}
 	goroot, err := findGOROOT()
 	if err != nil {
 		return "", fmt.Errorf("cannot find go tool: %w", err)
 	}
 	path := filepath.Join(goroot, "bin", "go"+exeSuffix)
 	if _, err := os.Stat(path); err == nil {
 		return path, nil
 	}
 	goBin, err := exec.LookPath("go" + exeSuffix)
 	if err != nil {
 		return "", errors.New("cannot find go tool: " + err.Error())
 	}
 	return goBin, nil
 }

 // HasExec reports whether the current system can start new processes
 // using os.StartProcess or (more commonly) exec.Command.
 func HasExec() bool {
 	switch runtime.GOOS {
 	case "js", "ios":
 		return false
 	}
 	return true
 }

 // HasSrc reports whether the entire source tree is available under GOROOT.
 func HasSrc() bool {
 	switch runtime.GOOS {
 	case "ios":
 		return false
 	}
 	return true
 }

 // MustHaveExec checks that the current system can start new processes
 // using os.StartProcess or (more commonly) exec.Command.
 // If not, MustHaveExec calls t.Skip with an explanation.
 func MustHaveExec(t testing.TB) {
 	if !HasExec() {
 		t.Skipf("skipping test: cannot exec subprocess on %s/%s", runtime.GOOS, runtime.GOARCH)
 	}
 }

 var execPaths sync.Map // path -> error

 // MustHaveExecPath checks that the current system can start the named executable
 // using os.StartProcess or (more commonly) exec.Command.
 // If not, MustHaveExecPath calls t.Skip with an explanation.
 func MustHaveExecPath(t testing.TB, path string) {
 	MustHaveExec(t)

 	err, found := execPaths.Load(path)
 	if !found {
 		_, err = exec.LookPath(path)
 		err, _ = execPaths.LoadOrStore(path, err)
 	}
 	if err != nil {
 		t.Skipf("skipping test: %s: %s", path, err)
 	}
 }

 // HasExternalNetwork reports whether the current system can use
 // external (non-localhost) networks.
 func HasExternalNetwork() bool {
 	return !testing.Short() && runtime.GOOS != "js"
 }

 // MustHaveExternalNetwork checks that the current system can use
 // external (non-localhost) networks.
 // If not, MustHaveExternalNetwork calls t.Skip with an explanation.
 func MustHaveExternalNetwork(t testing.TB) {
 	if runtime.GOOS == "js" {
 		t.Skipf("skipping test: no external network on %s", runtime.GOOS)
 	}
 	if testing.Short() {
 		t.Skipf("skipping test: no external network in -short mode")
 	}
 }

 var haveCGO bool

 // HasCGO reports whether the current system can use cgo.
 func HasCGO() bool {
 	return haveCGO
 }

 // MustHaveCGO calls t.Skip if cgo is not available.
 func MustHaveCGO(t testing.TB) {
 	if !haveCGO {
 		t.Skipf("skipping test: no cgo")
 	}
 }

 // CanInternalLink reports whether the current system can link programs with
 // internal linking.
 // (This is the opposite of cmd/internal/sys.MustLinkExternal. Keep them in sync.)
 func CanInternalLink() bool {
 	switch runtime.GOOS {
 	case "android":
 		if runtime.GOARCH != "arm64" {
 			return false
 		}
 	case "ios":
 		if runtime.GOARCH == "arm64" {
 			return false
 		}
 	}
 	return true
 }

 // MustInternalLink checks that the current system can link programs with internal
 // linking.
 // If not, MustInternalLink calls t.Skip with an explanation.
 func MustInternalLink(t testing.TB) {
 	if !CanInternalLink() {
 		t.Skipf("skipping test: internal linking on %s/%s is not supported", runtime.GOOS, runtime.GOARCH)
 	}
 }

 // HasSymlink reports whether the current system can use os.Symlink.
 func HasSymlink() bool {
 	ok, _ := hasSymlink()
 	return ok
 }

 // MustHaveSymlink reports whether the current system can use os.Symlink.
 // If not, MustHaveSymlink calls t.Skip with an explanation.
 func MustHaveSymlink(t testing.TB) {
 	ok, reason := hasSymlink()
 	if !ok {
 		t.Skipf("skipping test: cannot make symlinks on %s/%s%s", runtime.GOOS, runtime.GOARCH, reason)
 	}
 }

 // HasLink reports whether the current system can use os.Link.
 func HasLink() bool {
 	// From Android release M (Marshmallow), hard linking files is blocked
 	// and an attempt to call link() on a file will return EACCES.
 	// - https://code.google.com/p/android-developer-preview/issues/detail?id=3150
 	return runtime.GOOS != "plan9" && runtime.GOOS != "android"
 }

 // MustHaveLink reports whether the current system can use os.Link.
 // If not, MustHaveLink calls t.Skip with an explanation.
 func MustHaveLink(t testing.TB) {
 	if !HasLink() {
 		t.Skipf("skipping test: hardlinks are not supported on %s/%s", runtime.GOOS, runtime.GOARCH)
 	}
 }

 var flaky = flag.Bool("flaky", false, "run known-flaky tests too")

 func SkipFlaky(t testing.TB, issue int) {
 	t.Helper()
 	if !*flaky {
 		t.Skipf("skipping known flaky test without the -flaky flag; see golang.org/issue/%d", issue)
 	}
 }

 func SkipFlakyNet(t testing.TB) {
 	t.Helper()
 	if v, _ := strconv.ParseBool(os.Getenv("GO_BUILDER_FLAKY_NET")); v {
 		t.Skip("skipping test on builder known to have frequent network failures")
 	}
 }

 // CleanCmdEnv will fill cmd.Env with the environment, excluding certain
 // variables that could modify the behavior of the Go tools such as
 // GODEBUG and GOTRACEBACK.
 func CleanCmdEnv(cmd *exec.Cmd) *exec.Cmd {
 	if cmd.Env != nil {
 		panic("environment already set")
 	}
 	for _, env := range os.Environ() {
 		// Exclude GODEBUG from the environment to prevent its output
 		// from breaking tests that are trying to parse other command output.
 		if strings.HasPrefix(env, "GODEBUG=") {
 			continue
 		}
 		// Exclude GOTRACEBACK for the same reason.
 		if strings.HasPrefix(env, "GOTRACEBACK=") {
 			continue
 		}
 		cmd.Env = append(cmd.Env, env)
 	}
 	return cmd
 }

 // CPUIsSlow reports whether the CPU running the test is suspected to be slow.
 func CPUIsSlow() bool {
 	switch runtime.GOARCH {
 	case "arm", "mips", "mipsle", "mips64", "mips64le":
 		return true
 	}
 	return false
 }

 // SkipIfShortAndSlow skips t if -short is set and the CPU running the test is
 // suspected to be slow.
 //
 // (This is useful for CPU-intensive tests that otherwise complete quickly.)
 func SkipIfShortAndSlow(t testing.TB) {
 	if testing.Short() && CPUIsSlow() {
 		t.Helper()
 		t.Skipf("skipping test in -short mode on %s", runtime.GOARCH)
 	}
 }

 // RunWithTimeout runs cmd and returns its combined output. If the
 // subprocess exits with a non-zero status, it will log that status
 // and return a non-nil error, but this is not considered fatal.
 func RunWithTimeout(t testing.TB, cmd *exec.Cmd) ([]byte, error) {
 	args := cmd.Args
 	if args == nil {
 		args = []string{cmd.Path}
 	}

 	var b bytes.Buffer
 	cmd.Stdout = &b
 	cmd.Stderr = &b
 	if err := cmd.Start(); err != nil {
 		t.Fatalf("starting %s: %v", args, err)
 	}

 	// If the process doesn't complete within 1 minute,
 	// assume it is hanging and kill it to get a stack trace.
 	p := cmd.Process
 	done := make(chan bool)
 	go func() {
 		scale := 1
 		// This GOARCH/GOOS test is copied from cmd/dist/test.go.
 		// TODO(iant): Have cmd/dist update the environment variable.
 		if runtime.GOARCH == "arm" || runtime.GOOS == "windows" {
 			scale = 2
 		}
 		if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
 			if sc, err := strconv.Atoi(s); err == nil {
 				scale = sc
 			}
 		}

 		select {
 		case <-done:
 		case <-time.After(time.Duration(scale) * time.Minute):
 			p.Signal(Sigquit)
 			// If SIGQUIT doesn't do it after a little
 			// while, kill the process.
 			select {
 			case <-done:
 			case <-time.After(time.Duration(scale) * 30 * time.Second):
 				p.Signal(os.Kill)
 			}
 		}
 	}()

 	err := cmd.Wait()
 	if err != nil {
 		t.Logf("%s exit status: %v", args, err)
 	}
 	close(done)

 	return b.Bytes(), err
 }
	// Copyright 2015 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 testenv provides information about what functionality
	// is available in different testing environments run by the Go team.
	//
	// It is an internal package because these details are specific
	// to the Go team's test setup (on build.golang.org) and not
	// fundamental to tests in general.
	package testenv

	import (
	"bytes"
	"errors"
	"flag"
	"fmt"
	"internal/cfg"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"testing"
	"time"
	)

	// Builder reports the name of the builder running this test
	// (for example, "linux-amd64" or "windows-386-gce").
	// If the test is not running on the build infrastructure,
	// Builder returns the empty string.
	func Builder() string {
	return os.Getenv("GO_BUILDER_NAME")
	}

	// HasGoBuild reports whether the current system can build programs with “go build”
	// and then run them with os.StartProcess or exec.Command.
	func HasGoBuild() bool {
	if os.Getenv("GO_GCFLAGS") != "" {
	// It's too much work to require every caller of the go command
	// to pass along "-gcflags="+os.Getenv("GO_GCFLAGS").
	// For now, if $GO_GCFLAGS is set, report that we simply can't
	// run go build.
	return false
	}
	switch runtime.GOOS {
	case "android", "js", "ios":
	return false
	}
	return true
	}

	// MustHaveGoBuild checks that the current system can build programs with “go build”
	// and then run them with os.StartProcess or exec.Command.
	// If not, MustHaveGoBuild calls t.Skip with an explanation.
	func MustHaveGoBuild(t testing.TB) {
	if os.Getenv("GO_GCFLAGS") != "" {
	t.Skipf("skipping test: 'go build' not compatible with setting $GO_GCFLAGS")
	}
	if !HasGoBuild() {
	t.Skipf("skipping test: 'go build' not available on %s/%s", runtime.GOOS, runtime.GOARCH)
	}
	}

	// HasGoRun reports whether the current system can run programs with “go run.”
	func HasGoRun() bool {
	// For now, having go run and having go build are the same.
	return HasGoBuild()
	}

	// MustHaveGoRun checks that the current system can run programs with “go run.”
	// If not, MustHaveGoRun calls t.Skip with an explanation.
	func MustHaveGoRun(t testing.TB) {
	if !HasGoRun() {
	t.Skipf("skipping test: 'go run' not available on %s/%s", runtime.GOOS, runtime.GOARCH)
	}
	}

	// GoToolPath reports the path to the Go tool.
	// It is a convenience wrapper around GoTool.
	// If the tool is unavailable GoToolPath calls t.Skip.
	// If the tool should be available and isn't, GoToolPath calls t.Fatal.
	func GoToolPath(t testing.TB) string {
	MustHaveGoBuild(t)
	path, err := GoTool()
	if err != nil {
	t.Fatal(err)
	}
	// Add all environment variables that affect the Go command to test metadata.
	// Cached test results will be invalidate when these variables change.
	// See golang.org/issue/32285.
	for _, envVar := range strings.Fields(cfg.KnownEnv) {
	os.Getenv(envVar)
	}
	return path
	}

	var (
	gorootOnce sync.Once
	gorootPath string
	gorootErr error
	)

	func findGOROOT() (string, error) {
	gorootOnce.Do(func() {
	gorootPath = runtime.GOROOT()
	if gorootPath != "" {
	// If runtime.GOROOT() is non-empty, assume that it is valid.
	//
	// (It might not be: for example, the user may have explicitly set GOROOT
	// to the wrong directory, or explicitly set GOROOT_FINAL but not GOROOT
	// and hasn't moved the tree to GOROOT_FINAL yet. But those cases are
	// rare, and if that happens the user can fix what they broke.)
	return
	}

	// runtime.GOROOT doesn't know where GOROOT is (perhaps because the test
	// binary was built with -trimpath, or perhaps because GOROOT_FINAL was set
	// without GOROOT and the tree hasn't been moved there yet).
	//
	// Since this is internal/testenv, we can cheat and assume that the caller
	// is a test of some package in a subdirectory of GOROOT/src. ('go test'
	// runs the test in the directory containing the packaged under test.) That
	// means that if we start walking up the tree, we should eventually find
	// GOROOT/src/go.mod, and we can report the parent directory of that.

	cwd, err := os.Getwd()
	if err != nil {
	gorootErr = fmt.Errorf("finding GOROOT: %w", err)
	return
	}

	dir := cwd
	for {
	parent := filepath.Dir(dir)
	if parent == dir {
	// dir is either "." or only a volume name.
	gorootErr = fmt.Errorf("failed to locate GOROOT/src in any parent directory")
	return
	}

	if base := filepath.Base(dir); base != "src" {
	dir = parent
	continue // dir cannot be GOROOT/src if it doesn't end in "src".
	}

	b, err := os.ReadFile(filepath.Join(dir, "go.mod"))
	if err != nil {
	if os.IsNotExist(err) {
	dir = parent
	continue
	}
	gorootErr = fmt.Errorf("finding GOROOT: %w", err)
	return
	}
	goMod := string(b)

	for goMod != "" {
	var line string
	line, goMod, _ = strings.Cut(goMod, "\n")
	fields := strings.Fields(line)
	if len(fields) >= 2 && fields[0] == "module" && fields[1] == "std" {
	// Found "module std", which is the module declaration in GOROOT/src!
	gorootPath = parent
	return
	}
	}
	}
	})

	return gorootPath, gorootErr
	}

	// GOROOT reports the path to the directory containing the root of the Go
	// project source tree. This is normally equivalent to runtime.GOROOT, but
	// works even if the test binary was built with -trimpath.
	//
	// If GOROOT cannot be found, GOROOT skips t if t is non-nil,
	// or panics otherwise.
	func GOROOT(t testing.TB) string {
	path, err := findGOROOT()
	if err != nil {
	if t == nil {
	panic(err)
	}
	t.Helper()
	t.Skip(err)
	}
	return path
	}

	// GoTool reports the path to the Go tool.
	func GoTool() (string, error) {
	if !HasGoBuild() {
	return "", errors.New("platform cannot run go tool")
	}
	var exeSuffix string
	if runtime.GOOS == "windows" {
	exeSuffix = ".exe"
	}
	goroot, err := findGOROOT()
	if err != nil {
	return "", fmt.Errorf("cannot find go tool: %w", err)
	}
	path := filepath.Join(goroot, "bin", "go"+exeSuffix)
	if _, err := os.Stat(path); err == nil {
	return path, nil
	}
	goBin, err := exec.LookPath("go" + exeSuffix)
	if err != nil {
	return "", errors.New("cannot find go tool: " + err.Error())
	}
	return goBin, nil
	}

	// HasExec reports whether the current system can start new processes
	// using os.StartProcess or (more commonly) exec.Command.
	func HasExec() bool {
	switch runtime.GOOS {
	case "js", "ios":
	return false
	}
	return true
	}

	// HasSrc reports whether the entire source tree is available under GOROOT.
	func HasSrc() bool {
	switch runtime.GOOS {
	case "ios":
	return false
	}
	return true
	}

	// MustHaveExec checks that the current system can start new processes
	// using os.StartProcess or (more commonly) exec.Command.
	// If not, MustHaveExec calls t.Skip with an explanation.
	func MustHaveExec(t testing.TB) {
	if !HasExec() {
	t.Skipf("skipping test: cannot exec subprocess on %s/%s", runtime.GOOS, runtime.GOARCH)
	}
	}

	var execPaths sync.Map // path -> error

	// MustHaveExecPath checks that the current system can start the named executable
	// using os.StartProcess or (more commonly) exec.Command.
	// If not, MustHaveExecPath calls t.Skip with an explanation.
	func MustHaveExecPath(t testing.TB, path string) {
	MustHaveExec(t)

	err, found := execPaths.Load(path)
	if !found {
	_, err = exec.LookPath(path)
	err, _ = execPaths.LoadOrStore(path, err)
	}
	if err != nil {
	t.Skipf("skipping test: %s: %s", path, err)
	}
	}

	// HasExternalNetwork reports whether the current system can use
	// external (non-localhost) networks.
	func HasExternalNetwork() bool {
	return !testing.Short() && runtime.GOOS != "js"
	}

	// MustHaveExternalNetwork checks that the current system can use
	// external (non-localhost) networks.
	// If not, MustHaveExternalNetwork calls t.Skip with an explanation.
	func MustHaveExternalNetwork(t testing.TB) {
	if runtime.GOOS == "js" {
	t.Skipf("skipping test: no external network on %s", runtime.GOOS)
	}
	if testing.Short() {
	t.Skipf("skipping test: no external network in -short mode")
	}
	}

	var haveCGO bool

	// HasCGO reports whether the current system can use cgo.
	func HasCGO() bool {
	return haveCGO
	}

	// MustHaveCGO calls t.Skip if cgo is not available.
	func MustHaveCGO(t testing.TB) {
	if !haveCGO {
	t.Skipf("skipping test: no cgo")
	}
	}

	// CanInternalLink reports whether the current system can link programs with
	// internal linking.
	// (This is the opposite of cmd/internal/sys.MustLinkExternal. Keep them in sync.)
	func CanInternalLink() bool {
	switch runtime.GOOS {
	case "android":
	if runtime.GOARCH != "arm64" {
	return false
	}
	case "ios":
	if runtime.GOARCH == "arm64" {
	return false
	}
	}
	return true
	}

	// MustInternalLink checks that the current system can link programs with internal
	// linking.
	// If not, MustInternalLink calls t.Skip with an explanation.
	func MustInternalLink(t testing.TB) {
	if !CanInternalLink() {
	t.Skipf("skipping test: internal linking on %s/%s is not supported", runtime.GOOS, runtime.GOARCH)
	}
	}

	// HasSymlink reports whether the current system can use os.Symlink.
	func HasSymlink() bool {
	ok, _ := hasSymlink()
	return ok
	}

	// MustHaveSymlink reports whether the current system can use os.Symlink.
	// If not, MustHaveSymlink calls t.Skip with an explanation.
	func MustHaveSymlink(t testing.TB) {
	ok, reason := hasSymlink()
	if !ok {
	t.Skipf("skipping test: cannot make symlinks on %s/%s%s", runtime.GOOS, runtime.GOARCH, reason)
	}
	}

	// HasLink reports whether the current system can use os.Link.
	func HasLink() bool {
	// From Android release M (Marshmallow), hard linking files is blocked
	// and an attempt to call link() on a file will return EACCES.
	// - https://code.google.com/p/android-developer-preview/issues/detail?id=3150
	return runtime.GOOS != "plan9" && runtime.GOOS != "android"
	}

	// MustHaveLink reports whether the current system can use os.Link.
	// If not, MustHaveLink calls t.Skip with an explanation.
	func MustHaveLink(t testing.TB) {
	if !HasLink() {
	t.Skipf("skipping test: hardlinks are not supported on %s/%s", runtime.GOOS, runtime.GOARCH)
	}
	}

	var flaky = flag.Bool("flaky", false, "run known-flaky tests too")

	func SkipFlaky(t testing.TB, issue int) {
	t.Helper()
	if !*flaky {
	t.Skipf("skipping known flaky test without the -flaky flag; see golang.org/issue/%d", issue)
	}
	}

	func SkipFlakyNet(t testing.TB) {
	t.Helper()
	if v, _ := strconv.ParseBool(os.Getenv("GO_BUILDER_FLAKY_NET")); v {
	t.Skip("skipping test on builder known to have frequent network failures")
	}
	}

	// CleanCmdEnv will fill cmd.Env with the environment, excluding certain
	// variables that could modify the behavior of the Go tools such as
	// GODEBUG and GOTRACEBACK.
	func CleanCmdEnv(cmd exec.Cmd) exec.Cmd {
	if cmd.Env != nil {
	panic("environment already set")
	}
	for _, env := range os.Environ() {
	// Exclude GODEBUG from the environment to prevent its output
	// from breaking tests that are trying to parse other command output.
	if strings.HasPrefix(env, "GODEBUG=") {
	continue
	}
	// Exclude GOTRACEBACK for the same reason.
	if strings.HasPrefix(env, "GOTRACEBACK=") {
	continue
	}
	cmd.Env = append(cmd.Env, env)
	}
	return cmd
	}

	// CPUIsSlow reports whether the CPU running the test is suspected to be slow.
	func CPUIsSlow() bool {
	switch runtime.GOARCH {
	case "arm", "mips", "mipsle", "mips64", "mips64le":
	return true
	}
	return false
	}

	// SkipIfShortAndSlow skips t if -short is set and the CPU running the test is
	// suspected to be slow.
	//
	// (This is useful for CPU-intensive tests that otherwise complete quickly.)
	func SkipIfShortAndSlow(t testing.TB) {
	if testing.Short() && CPUIsSlow() {
	t.Helper()
	t.Skipf("skipping test in -short mode on %s", runtime.GOARCH)
	}
	}

	// RunWithTimeout runs cmd and returns its combined output. If the
	// subprocess exits with a non-zero status, it will log that status
	// and return a non-nil error, but this is not considered fatal.
	func RunWithTimeout(t testing.TB, cmd *exec.Cmd) ([]byte, error) {
	args := cmd.Args
	if args == nil {
	args = []string{cmd.Path}
	}

	var b bytes.Buffer
	cmd.Stdout = &b
	cmd.Stderr = &b
	if err := cmd.Start(); err != nil {
	t.Fatalf("starting %s: %v", args, err)
	}

	// If the process doesn't complete within 1 minute,
	// assume it is hanging and kill it to get a stack trace.
	p := cmd.Process
	done := make(chan bool)
	go func() {
	scale := 1
	// This GOARCH/GOOS test is copied from cmd/dist/test.go.
	// TODO(iant): Have cmd/dist update the environment variable.
	if runtime.GOARCH == "arm" \|\| runtime.GOOS == "windows" {
	scale = 2
	}
	if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
	if sc, err := strconv.Atoi(s); err == nil {
	scale = sc
	}
	}

	select {
	case <-done:
	case <-time.After(time.Duration(scale) * time.Minute):
	p.Signal(Sigquit)
	// If SIGQUIT doesn't do it after a little
	// while, kill the process.
	select {
	case <-done:
	case <-time.After(time.Duration(scale) * 30 * time.Second):
	p.Signal(os.Kill)
	}
	}
	}()

	err := cmd.Wait()
	if err != nil {
	t.Logf("%s exit status: %v", args, err)
	}
	close(done)

	return b.Bytes(), err
	}