sandbox.go - playground - Git at Google

 // Copyright 2014 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.

 // TODO(andybons): add logging
 // TODO(andybons): restrict memory use
 // TODO(andybons): send exit code to user

 package main

 import (
 	"bytes"
 	"context"
 	"crypto/sha256"
 	"encoding/json"
 	"fmt"
 	"go/ast"
 	"go/parser"
 	"go/token"
 	"io"
 	"io/ioutil"
 	stdlog "log"
 	"net/http"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"text/template"
 	"time"

 	"github.com/bradfitz/gomemcache/memcache"
 )

 const (
 	maxRunTime = 2 * time.Second

 	// progName is the program name in compiler errors
 	progName = "prog.go"
 )

 type request struct {
 	Body string
 }

 type response struct {
 	Errors string
 	Events []Event
 }

 func (s *server) handleCompile(w http.ResponseWriter, r *http.Request) {
 	var req request
 	// Until programs that depend on golang.org/x/tools/godoc/static/playground.js
 	// are updated to always send JSON, this check is in place.
 	if b := r.FormValue("body"); b != "" {
 		req.Body = b
 	} else if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
 		http.Error(w, fmt.Sprintf("error decoding request: %v", err), http.StatusBadRequest)
 		return
 	}

 	resp := &response{}
 	key := cacheKey(req.Body)
 	if err := s.cache.Get(key, resp); err != nil {
 		if err != memcache.ErrCacheMiss {
 			s.log.Errorf("s.cache.Get(%q, &response): %v", key, err)
 		}
 		var err error
 		resp, err = s.compileAndRun(&req)
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
 		}
 		if err := s.cache.Set(key, resp); err != nil {
 			s.log.Errorf("cache.Set(%q, resp): %v", key, err)
 		}
 	}

 	var buf bytes.Buffer
 	if err := json.NewEncoder(&buf).Encode(resp); err != nil {
 		http.Error(w, fmt.Sprintf("error encoding response: %v", err), http.StatusInternalServerError)
 		return
 	}
 	if _, err := io.Copy(w, &buf); err != nil {
 		s.log.Errorf("io.Copy(w, %+v): %v", buf, err)
 		return
 	}
 }

 func cacheKey(body string) string {
 	h := sha256.New()
 	io.WriteString(h, body)
 	return fmt.Sprintf("prog-%s-%x", runtime.Version(), h.Sum(nil))
 }

 // isTestFunc tells whether fn has the type of a testing function.
 func isTestFunc(fn *ast.FuncDecl) bool {
 	if fn.Type.Results != nil && len(fn.Type.Results.List) > 0 ||
 		fn.Type.Params.List == nil ||
 		len(fn.Type.Params.List) != 1 ||
 		len(fn.Type.Params.List[0].Names) > 1 {
 		return false
 	}
 	ptr, ok := fn.Type.Params.List[0].Type.(*ast.StarExpr)
 	if !ok {
 		return false
 	}
 	// We can't easily check that the type is *testing.T
 	// because we don't know how testing has been imported,
 	// but at least check that it's *T or *something.T.
 	if name, ok := ptr.X.(*ast.Ident); ok && name.Name == "T" {
 		return true
 	}
 	if sel, ok := ptr.X.(*ast.SelectorExpr); ok && sel.Sel.Name == "T" {
 		return true
 	}
 	return false
 }

 // isTest tells whether name looks like a test (or benchmark, according to prefix).
 // It is a Test (say) if there is a character after Test that is not a lower-case letter.
 // We don't want TesticularCancer.
 func isTest(name, prefix string) bool {
 	if !strings.HasPrefix(name, prefix) {
 		return false
 	}
 	if len(name) == len(prefix) { // "Test" is ok
 		return true
 	}
 	return ast.IsExported(name[len(prefix):])
 }

 // getTestMain returns sources with main function which runs all found tests in src.
 // This happens if the main function is not present and there are appropriate test functions.
 // Otherwise it returns nil.
 // Examples are not supported yet. Benchmarks will never be supported because of sandboxing.
 func getTestMain(src []byte) []byte {
 	fset := token.NewFileSet()
 	// Early bail for most cases.
 	f, err := parser.ParseFile(fset, "main.go", src, parser.ImportsOnly)
 	if err != nil || f.Name.Name != "main" {
 		return nil
 	}
 	var testing bool
 	for _, s := range f.Imports {
 		if s.Path.Value == `"testing"` && s.Name == nil {
 			testing = true
 			break
 		}
 	}
 	if !testing {
 		return nil
 	}

 	// Parse everything and extract test names
 	f, err = parser.ParseFile(fset, "main.go", src, parser.ParseComments)
 	if err != nil {
 		return nil
 	}

 	var tests []string
 	for _, d := range f.Decls {
 		n, ok := d.(*ast.FuncDecl)
 		if !ok {
 			continue
 		}
 		name := n.Name.Name
 		switch {
 		case name == "main":
 			// main declared a method will not obstruct creation of our main function.
 			if n.Recv == nil {
 				return nil
 			}
 		case isTest(name, "Test") && isTestFunc(n):
 			tests = append(tests, name)
 		}
 	}

 	if len(tests) == 0 {
 		return nil
 	}
 	code := new(bytes.Buffer)
 	if err := testTmpl.Execute(code, tests); err != nil {
 		panic(err)
 	}
 	return code.Bytes()
 }

 var testTmpl = template.Must(template.New("main").Parse(`
 func main() {
 	matchAll := func(t string, pat string) (bool, error) { return true, nil }
 	tests := []testing.InternalTest{
 {{range .}}
 		{"{{.}}", {{.}}},
 {{end}}
 	}
 	testing.Main(matchAll, tests, nil, nil)
 }
 `))

 func (s *server) compileAndRun(req *request) (*response, error) {
 	// TODO(andybons): Add semaphore to limit number of running programs at once.
 	tmpDir, err := ioutil.TempDir("", "sandbox")
 	if err != nil {
 		return nil, fmt.Errorf("error creating temp directory: %v", err)
 	}
 	defer os.RemoveAll(tmpDir)

 	src := []byte(req.Body)
 	in := filepath.Join(tmpDir, "main.go")
 	if err := ioutil.WriteFile(in, src, 0400); err != nil {
 		return nil, fmt.Errorf("error creating temp file %q: %v", in, err)
 	}

 	fset := token.NewFileSet()

 	f, err := parser.ParseFile(fset, in, nil, parser.PackageClauseOnly)
 	if err == nil && f.Name.Name != "main" {
 		return &response{Errors: "package name must be main"}, nil
 	}

 	var testParam string
 	if code := getTestMain(src); code != nil {
 		testParam = "-test.v"
 		src = append(src, code...)
 		if err := ioutil.WriteFile(in, src, 0400); err != nil {
 			return nil, fmt.Errorf("error creating temp file %q: %v", in, err)
 		}
 	}

 	exe := filepath.Join(tmpDir, "a.out")
 	cmd := exec.Command("go", "build", "-o", exe, in)
 	cmd.Env = []string{"GOOS=nacl", "GOARCH=amd64p32", "GOPATH=" + os.Getenv("GOPATH")}
 	if out, err := cmd.CombinedOutput(); err != nil {
 		if _, ok := err.(*exec.ExitError); ok {
 			// Return compile errors to the user.

 			// Rewrite compiler errors to refer to progName
 			// instead of '/tmp/sandbox1234/main.go'.
 			errs := strings.Replace(string(out), in, progName, -1)

 			// "go build", invoked with a file name, puts this odd
 			// message before any compile errors; strip it.
 			errs = strings.Replace(errs, "# command-line-arguments\n", "", 1)

 			return &response{Errors: errs}, nil
 		}
 		return nil, fmt.Errorf("error building go source: %v", err)
 	}
 	ctx, cancel := context.WithTimeout(context.Background(), maxRunTime)
 	defer cancel()
 	cmd = exec.CommandContext(ctx, "sel_ldr_x86_64", "-l", "/dev/null", "-S", "-e", exe, testParam)
 	rec := new(Recorder)
 	cmd.Stdout = rec.Stdout()
 	cmd.Stderr = rec.Stderr()
 	if err := cmd.Run(); err != nil {
 		if ctx.Err() == context.DeadlineExceeded {
 			return &response{Errors: "process took too long"}, nil
 		}
 		if _, ok := err.(*exec.ExitError); !ok {
 			return nil, fmt.Errorf("error running sandbox: %v", err)
 		}
 	}
 	events, err := rec.Events()
 	if err != nil {
 		return nil, fmt.Errorf("error decoding events: %v", err)
 	}
 	return &response{Events: events}, nil
 }

 func (s *server) healthCheck() error {
 	resp, err := s.compileAndRun(&request{Body: healthProg})
 	if err != nil {
 		return err
 	}
 	if resp.Errors != "" {
 		return fmt.Errorf("compile error: %v", resp.Errors)
 	}
 	if len(resp.Events) != 1 || resp.Events[0].Message != "ok" {
 		return fmt.Errorf("unexpected output: %v", resp.Events)
 	}
 	return nil
 }

 const healthProg = `
 package main

 import "fmt"

 func main() { fmt.Print("ok") }
 `

 func (s *server) test() {
 	if err := s.healthCheck(); err != nil {
 		stdlog.Fatal(err)
 	}
 	for _, t := range tests {
 		resp, err := s.compileAndRun(&request{Body: t.prog})
 		if err != nil {
 			stdlog.Fatal(err)
 		}
 		if t.errors != "" {
 			if resp.Errors != t.errors {
 				stdlog.Fatalf("resp.Errors = %q, want %q", resp.Errors, t.errors)
 			}
 			continue
 		}
 		if resp.Errors != "" {
 			stdlog.Fatal(resp.Errors)
 		}
 		if len(resp.Events) != 1 || !strings.Contains(resp.Events[0].Message, t.want) {
 			stdlog.Fatalf("unexpected output: %v, want %q", resp.Events, t.want)
 		}
 	}
 	fmt.Println("OK")
 }

 var tests = []struct {
 	prog, want, errors string
 }{
 	{prog: `
 package main

 import "time"

 func main() {
 	loc, err := time.LoadLocation("America/New_York")
 	if err != nil {
 		panic(err.Error())
 	}
 	println(loc.String())
 }
 `, want: "America/New_York"},

 	{prog: `
 package main

 import (
 	"fmt"
 	"time"
 )

 func main() {
 	fmt.Println(time.Now())
 }
 `, want: "2009-11-10 23:00:00 +0000 UTC"},

 	{prog: `
 package main

 import (
 	"fmt"
 	"time"
 )

 func main() {
 	t1 := time.Tick(time.Second * 3)
 	t2 := time.Tick(time.Second * 7)
 	t3 := time.Tick(time.Second * 11)
 	end := time.After(time.Second * 19)
 	want := "112131211"
 	var got []byte
 	for {
 		var c byte
 		select {
 		case <-t1:
 			c = '1'
 		case <-t2:
 			c = '2'
 		case <-t3:
 			c = '3'
 		case <-end:
 			if g := string(got); g != want {
 				fmt.Printf("got %q, want %q\n", g, want)
 			} else {
 				fmt.Println("timers fired as expected")
 			}
 			return
 		}
 		got = append(got, c)
 	}
 }
 `, want: "timers fired as expected"},

 	{prog: `
 package main

 import (
 	"code.google.com/p/go-tour/pic"
 	"code.google.com/p/go-tour/reader"
 	"code.google.com/p/go-tour/tree"
 	"code.google.com/p/go-tour/wc"
 )

 var (
 	_ = pic.Show
 	_ = reader.Validate
 	_ = tree.New
 	_ = wc.Test
 )

 func main() {
 	println("ok")
 }
 `, want: "ok"},
 	{prog: `
 package test

 func main() {
 	println("test")
 }
 `, want: "", errors: "package name must be main"},
 	{prog: `
 package main

 import (
 	"fmt"
 	"os"
 	"path/filepath"
 )

 func main() {
 	filepath.Walk("/", func(path string, info os.FileInfo, err error) error {
 		fmt.Println(path)
 		return nil
 	})
 }
 `, want: `/
 /dev
 /dev/null
 /dev/random
 /dev/urandom
 /dev/zero
 /etc
 /etc/group
 /etc/hosts
 /etc/passwd
 /etc/resolv.conf
 /tmp
 /usr
 /usr/local
 /usr/local/go
 /usr/local/go/lib
 /usr/local/go/lib/time
 /usr/local/go/lib/time/zoneinfo.zip`},
 	{prog: `
 package main

 import "testing"

 func TestSanity(t *testing.T) {
 	if 1+1 != 2 {
 		t.Error("uhh...")
 	}
 }
 `, want: `=== RUN   TestSanity
 --- PASS: TestSanity (0.00s)
 PASS`},

 	{prog: `
 package main

 func TestSanity(t *testing.T) {
 	t.Error("uhh...")
 }
 `, want: "", errors: "prog.go:4:20: undefined: testing\n"},

 	{prog: `
 package main

 import (
 	"fmt"
 	"testing"
 )

 func TestSanity(t *testing.T) {
 	t.Error("uhh...")
 }

 func main() {
 	fmt.Println("test")
 }
 `, want: "test"},
 }
	// Copyright 2014 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.

	// TODO(andybons): add logging
	// TODO(andybons): restrict memory use
	// TODO(andybons): send exit code to user

	package main

	import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"io"
	"io/ioutil"
	stdlog "log"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"text/template"
	"time"

	"github.com/bradfitz/gomemcache/memcache"
	)

	const (
	maxRunTime = 2 * time.Second

	// progName is the program name in compiler errors
	progName = "prog.go"
	)

	type request struct {
	Body string
	}

	type response struct {
	Errors string
	Events []Event
	}

	func (s server) handleCompile(w http.ResponseWriter, r http.Request) {
	var req request
	// Until programs that depend on golang.org/x/tools/godoc/static/playground.js
	// are updated to always send JSON, this check is in place.
	if b := r.FormValue("body"); b != "" {
	req.Body = b
	} else if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
	http.Error(w, fmt.Sprintf("error decoding request: %v", err), http.StatusBadRequest)
	return
	}

	resp := &response{}
	key := cacheKey(req.Body)
	if err := s.cache.Get(key, resp); err != nil {
	if err != memcache.ErrCacheMiss {
	s.log.Errorf("s.cache.Get(%q, &response): %v", key, err)
	}
	var err error
	resp, err = s.compileAndRun(&req)
	if err != nil {
	http.Error(w, err.Error(), http.StatusInternalServerError)
	return
	}
	if err := s.cache.Set(key, resp); err != nil {
	s.log.Errorf("cache.Set(%q, resp): %v", key, err)
	}
	}

	var buf bytes.Buffer
	if err := json.NewEncoder(&buf).Encode(resp); err != nil {
	http.Error(w, fmt.Sprintf("error encoding response: %v", err), http.StatusInternalServerError)
	return
	}
	if _, err := io.Copy(w, &buf); err != nil {
	s.log.Errorf("io.Copy(w, %+v): %v", buf, err)
	return
	}
	}

	func cacheKey(body string) string {
	h := sha256.New()
	io.WriteString(h, body)
	return fmt.Sprintf("prog-%s-%x", runtime.Version(), h.Sum(nil))
	}

	// isTestFunc tells whether fn has the type of a testing function.
	func isTestFunc(fn *ast.FuncDecl) bool {
	if fn.Type.Results != nil && len(fn.Type.Results.List) > 0 \|\|
	fn.Type.Params.List == nil \|\|
	len(fn.Type.Params.List) != 1 \|\|
	len(fn.Type.Params.List[0].Names) > 1 {
	return false
	}
	ptr, ok := fn.Type.Params.List[0].Type.(*ast.StarExpr)
	if !ok {
	return false
	}
	// We can't easily check that the type is *testing.T
	// because we don't know how testing has been imported,
	// but at least check that it's T or something.T.
	if name, ok := ptr.X.(*ast.Ident); ok && name.Name == "T" {
	return true
	}
	if sel, ok := ptr.X.(*ast.SelectorExpr); ok && sel.Sel.Name == "T" {
	return true
	}
	return false
	}

	// isTest tells whether name looks like a test (or benchmark, according to prefix).
	// It is a Test (say) if there is a character after Test that is not a lower-case letter.
	// We don't want TesticularCancer.
	func isTest(name, prefix string) bool {
	if !strings.HasPrefix(name, prefix) {
	return false
	}
	if len(name) == len(prefix) { // "Test" is ok
	return true
	}
	return ast.IsExported(name[len(prefix):])
	}

	// getTestMain returns sources with main function which runs all found tests in src.
	// This happens if the main function is not present and there are appropriate test functions.
	// Otherwise it returns nil.
	// Examples are not supported yet. Benchmarks will never be supported because of sandboxing.
	func getTestMain(src []byte) []byte {
	fset := token.NewFileSet()
	// Early bail for most cases.
	f, err := parser.ParseFile(fset, "main.go", src, parser.ImportsOnly)
	if err != nil \|\| f.Name.Name != "main" {
	return nil
	}
	var testing bool
	for _, s := range f.Imports {
	if s.Path.Value == `"testing"` && s.Name == nil {
	testing = true
	break
	}
	}
	if !testing {
	return nil
	}

	// Parse everything and extract test names
	f, err = parser.ParseFile(fset, "main.go", src, parser.ParseComments)
	if err != nil {
	return nil
	}

	var tests []string
	for _, d := range f.Decls {
	n, ok := d.(*ast.FuncDecl)
	if !ok {
	continue
	}
	name := n.Name.Name
	switch {
	case name == "main":
	// main declared a method will not obstruct creation of our main function.
	if n.Recv == nil {
	return nil
	}
	case isTest(name, "Test") && isTestFunc(n):
	tests = append(tests, name)
	}
	}

	if len(tests) == 0 {
	return nil
	}
	code := new(bytes.Buffer)
	if err := testTmpl.Execute(code, tests); err != nil {
	panic(err)
	}
	return code.Bytes()
	}

	var testTmpl = template.Must(template.New("main").Parse(`
	func main() {
	matchAll := func(t string, pat string) (bool, error) { return true, nil }
	tests := []testing.InternalTest{
	{{range .}}
	{"{{.}}", {{.}}},
	{{end}}
	}
	testing.Main(matchAll, tests, nil, nil)
	}
	`))

	func (s server) compileAndRun(req request) (*response, error) {
	// TODO(andybons): Add semaphore to limit number of running programs at once.
	tmpDir, err := ioutil.TempDir("", "sandbox")
	if err != nil {
	return nil, fmt.Errorf("error creating temp directory: %v", err)
	}
	defer os.RemoveAll(tmpDir)

	src := []byte(req.Body)
	in := filepath.Join(tmpDir, "main.go")
	if err := ioutil.WriteFile(in, src, 0400); err != nil {
	return nil, fmt.Errorf("error creating temp file %q: %v", in, err)
	}

	fset := token.NewFileSet()

	f, err := parser.ParseFile(fset, in, nil, parser.PackageClauseOnly)
	if err == nil && f.Name.Name != "main" {
	return &response{Errors: "package name must be main"}, nil
	}

	var testParam string
	if code := getTestMain(src); code != nil {
	testParam = "-test.v"
	src = append(src, code...)
	if err := ioutil.WriteFile(in, src, 0400); err != nil {
	return nil, fmt.Errorf("error creating temp file %q: %v", in, err)
	}
	}

	exe := filepath.Join(tmpDir, "a.out")
	cmd := exec.Command("go", "build", "-o", exe, in)
	cmd.Env = []string{"GOOS=nacl", "GOARCH=amd64p32", "GOPATH=" + os.Getenv("GOPATH")}
	if out, err := cmd.CombinedOutput(); err != nil {
	if _, ok := err.(*exec.ExitError); ok {
	// Return compile errors to the user.

	// Rewrite compiler errors to refer to progName
	// instead of '/tmp/sandbox1234/main.go'.
	errs := strings.Replace(string(out), in, progName, -1)

	// "go build", invoked with a file name, puts this odd
	// message before any compile errors; strip it.
	errs = strings.Replace(errs, "# command-line-arguments\n", "", 1)

	return &response{Errors: errs}, nil
	}
	return nil, fmt.Errorf("error building go source: %v", err)
	}
	ctx, cancel := context.WithTimeout(context.Background(), maxRunTime)
	defer cancel()
	cmd = exec.CommandContext(ctx, "sel_ldr_x86_64", "-l", "/dev/null", "-S", "-e", exe, testParam)
	rec := new(Recorder)
	cmd.Stdout = rec.Stdout()
	cmd.Stderr = rec.Stderr()
	if err := cmd.Run(); err != nil {
	if ctx.Err() == context.DeadlineExceeded {
	return &response{Errors: "process took too long"}, nil
	}
	if _, ok := err.(*exec.ExitError); !ok {
	return nil, fmt.Errorf("error running sandbox: %v", err)
	}
	}
	events, err := rec.Events()
	if err != nil {
	return nil, fmt.Errorf("error decoding events: %v", err)
	}
	return &response{Events: events}, nil
	}

	func (s *server) healthCheck() error {
	resp, err := s.compileAndRun(&request{Body: healthProg})
	if err != nil {
	return err
	}
	if resp.Errors != "" {
	return fmt.Errorf("compile error: %v", resp.Errors)
	}
	if len(resp.Events) != 1 \|\| resp.Events[0].Message != "ok" {
	return fmt.Errorf("unexpected output: %v", resp.Events)
	}
	return nil
	}

	const healthProg = `
	package main

	import "fmt"

	func main() { fmt.Print("ok") }
	`

	func (s *server) test() {
	if err := s.healthCheck(); err != nil {
	stdlog.Fatal(err)
	}
	for _, t := range tests {
	resp, err := s.compileAndRun(&request{Body: t.prog})
	if err != nil {
	stdlog.Fatal(err)
	}
	if t.errors != "" {
	if resp.Errors != t.errors {
	stdlog.Fatalf("resp.Errors = %q, want %q", resp.Errors, t.errors)
	}
	continue
	}
	if resp.Errors != "" {
	stdlog.Fatal(resp.Errors)
	}
	if len(resp.Events) != 1 \|\| !strings.Contains(resp.Events[0].Message, t.want) {
	stdlog.Fatalf("unexpected output: %v, want %q", resp.Events, t.want)
	}
	}
	fmt.Println("OK")
	}

	var tests = []struct {
	prog, want, errors string
	}{
	{prog: `
	package main

	import "time"

	func main() {
	loc, err := time.LoadLocation("America/New_York")
	if err != nil {
	panic(err.Error())
	}
	println(loc.String())
	}
	`, want: "America/New_York"},

	{prog: `
	package main

	import (
	"fmt"
	"time"
	)

	func main() {
	fmt.Println(time.Now())
	}
	`, want: "2009-11-10 23:00:00 +0000 UTC"},

	{prog: `
	package main

	import (
	"fmt"
	"time"
	)

	func main() {
	t1 := time.Tick(time.Second * 3)
	t2 := time.Tick(time.Second * 7)
	t3 := time.Tick(time.Second * 11)
	end := time.After(time.Second * 19)
	want := "112131211"
	var got []byte
	for {
	var c byte
	select {
	case <-t1:
	c = '1'
	case <-t2:
	c = '2'
	case <-t3:
	c = '3'
	case <-end:
	if g := string(got); g != want {
	fmt.Printf("got %q, want %q\n", g, want)
	} else {
	fmt.Println("timers fired as expected")
	}
	return
	}
	got = append(got, c)
	}
	}
	`, want: "timers fired as expected"},

	{prog: `
	package main

	import (
	"code.google.com/p/go-tour/pic"
	"code.google.com/p/go-tour/reader"
	"code.google.com/p/go-tour/tree"
	"code.google.com/p/go-tour/wc"
	)

	var (
	_ = pic.Show
	_ = reader.Validate
	_ = tree.New
	_ = wc.Test
	)

	func main() {
	println("ok")
	}
	`, want: "ok"},
	{prog: `
	package test

	func main() {
	println("test")
	}
	`, want: "", errors: "package name must be main"},
	{prog: `
	package main

	import (
	"fmt"
	"os"
	"path/filepath"
	)

	func main() {
	filepath.Walk("/", func(path string, info os.FileInfo, err error) error {
	fmt.Println(path)
	return nil
	})
	}
	`, want: `/
	/dev
	/dev/null
	/dev/random
	/dev/urandom
	/dev/zero
	/etc
	/etc/group
	/etc/hosts
	/etc/passwd
	/etc/resolv.conf
	/tmp
	/usr
	/usr/local
	/usr/local/go
	/usr/local/go/lib
	/usr/local/go/lib/time
	/usr/local/go/lib/time/zoneinfo.zip`},
	{prog: `
	package main

	import "testing"

	func TestSanity(t *testing.T) {
	if 1+1 != 2 {
	t.Error("uhh...")
	}
	}
	`, want: `=== RUN TestSanity
	--- PASS: TestSanity (0.00s)
	PASS`},

	{prog: `
	package main

	func TestSanity(t *testing.T) {
	t.Error("uhh...")
	}
	`, want: "", errors: "prog.go:4:20: undefined: testing\n"},

	{prog: `
	package main

	import (
	"fmt"
	"testing"
	)

	func TestSanity(t *testing.T) {
	t.Error("uhh...")
	}

	func main() {
	fmt.Println("test")
	}
	`, want: "test"},
	}