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// 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
import (
"context"
"errors"
"fmt"
"os"
"os/exec"
"runtime"
"strconv"
"strings"
"sync"
"testing"
"time"
)
// 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.
//
// On some platforms MustHaveExec checks for exec support by re-executing the
// current executable, which must be a binary built by 'go test'.
// We intentionally do not provide a HasExec function because of the risk of
// inappropriate recursion in TestMain functions.
//
// To check for exec support outside of a test, just try to exec the command.
// If exec is not supported, testenv.SyscallIsNotSupported will return true
// for the resulting error.
func MustHaveExec(t testing.TB) {
tryExecOnce.Do(func() {
tryExecErr = tryExec()
})
if tryExecErr != nil {
t.Skipf("skipping test: cannot exec subprocess on %s/%s: %v", runtime.GOOS, runtime.GOARCH, tryExecErr)
}
}
var (
tryExecOnce sync.Once
tryExecErr error
)
func tryExec() error {
switch runtime.GOOS {
case "wasip1", "js", "ios":
default:
// Assume that exec always works on non-mobile platforms and Android.
return nil
}
// ios has an exec syscall but on real iOS devices it might return a
// permission error. In an emulated environment (such as a Corellium host)
// it might succeed, so if we need to exec we'll just have to try it and
// find out.
//
// As of 2023-04-19 wasip1 and js don't have exec syscalls at all, but we
// may as well use the same path so that this branch can be tested without
// an ios environment.
if !testing.Testing() {
// This isn't a standard 'go test' binary, so we don't know how to
// self-exec in a way that should succeed without side effects.
// Just forget it.
return errors.New("can't probe for exec support with a non-test executable")
}
// We know that this is a test executable. We should be able to run it with a
// no-op flag to check for overall exec support.
exe, err := os.Executable()
if err != nil {
return fmt.Errorf("can't probe for exec support: %w", err)
}
cmd := exec.Command(exe, "-test.list=^$")
cmd.Env = origEnv
return cmd.Run()
}
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)
}
}
// 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
}
// CommandContext is like exec.CommandContext, but:
// - skips t if the platform does not support os/exec,
// - sends SIGQUIT (if supported by the platform) instead of SIGKILL
// in its Cancel function
// - if the test has a deadline, adds a Context timeout and WaitDelay
// for an arbitrary grace period before the test's deadline expires,
// - fails the test if the command does not complete before the test's deadline, and
// - sets a Cleanup function that verifies that the test did not leak a subprocess.
func CommandContext(t testing.TB, ctx context.Context, name string, args ...string) *exec.Cmd {
t.Helper()
MustHaveExec(t)
var (
cancelCtx context.CancelFunc
gracePeriod time.Duration // unlimited unless the test has a deadline (to allow for interactive debugging)
)
if t, ok := t.(interface {
testing.TB
Deadline() (time.Time, bool)
}); ok {
if td, ok := t.Deadline(); ok {
// Start with a minimum grace period, just long enough to consume the
// output of a reasonable program after it terminates.
gracePeriod = 100 * time.Millisecond
if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
scale, err := strconv.Atoi(s)
if err != nil {
t.Fatalf("invalid GO_TEST_TIMEOUT_SCALE: %v", err)
}
gracePeriod *= time.Duration(scale)
}
// If time allows, increase the termination grace period to 5% of the
// test's remaining time.
testTimeout := time.Until(td)
if gp := testTimeout / 20; gp > gracePeriod {
gracePeriod = gp
}
// When we run commands that execute subprocesses, we want to reserve two
// grace periods to clean up: one for the delay between the first
// termination signal being sent (via the Cancel callback when the Context
// expires) and the process being forcibly terminated (via the WaitDelay
// field), and a second one for the delay between the process being
// terminated and the test logging its output for debugging.
//
// (We want to ensure that the test process itself has enough time to
// log the output before it is also terminated.)
cmdTimeout := testTimeout - 2*gracePeriod
if cd, ok := ctx.Deadline(); !ok || time.Until(cd) > cmdTimeout {
// Either ctx doesn't have a deadline, or its deadline would expire
// after (or too close before) the test has already timed out.
// Add a shorter timeout so that the test will produce useful output.
ctx, cancelCtx = context.WithTimeout(ctx, cmdTimeout)
}
}
}
cmd := exec.CommandContext(ctx, name, args...)
cmd.Cancel = func() error {
if cancelCtx != nil && ctx.Err() == context.DeadlineExceeded {
// The command timed out due to running too close to the test's deadline.
// There is no way the test did that intentionally — it's too close to the
// wire! — so mark it as a test failure. That way, if the test expects the
// command to fail for some other reason, it doesn't have to distinguish
// between that reason and a timeout.
t.Errorf("test timed out while running command: %v", cmd)
} else {
// The command is being terminated due to ctx being canceled, but
// apparently not due to an explicit test deadline that we added.
// Log that information in case it is useful for diagnosing a failure,
// but don't actually fail the test because of it.
t.Logf("%v: terminating command: %v", ctx.Err(), cmd)
}
return cmd.Process.Signal(Sigquit)
}
cmd.WaitDelay = gracePeriod
t.Cleanup(func() {
if cancelCtx != nil {
cancelCtx()
}
if cmd.Process != nil && cmd.ProcessState == nil {
t.Errorf("command was started, but test did not wait for it to complete: %v", cmd)
}
})
return cmd
}
// Command is like exec.Command, but applies the same changes as
// testenv.CommandContext (with a default Context).
func Command(t testing.TB, name string, args ...string) *exec.Cmd {
t.Helper()
return CommandContext(t, context.Background(), name, args...)
}