import (
"bytes"
+ "context"
"errors"
"flag"
"fmt"
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
+// - adds a timeout (with an arbitrary grace period) before the test's deadline expires,
+// - sets a WaitDelay for an arbitrary grace period,
+// - 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 (
+ gracePeriod = 100 * time.Millisecond
+ cancel context.CancelFunc
+ )
+ 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 t, ok := t.(interface {
+ testing.TB
+ Deadline() (time.Time, bool)
+ }); ok {
+ if td, ok := t.Deadline(); ok {
+ if cd, ok := ctx.Deadline(); !ok || cd.Sub(td) > gracePeriod {
+ // Either ctx doesn't have a deadline, or its deadline would expire
+ // after (or too close before) the test has already timed out.
+ // Compute a new timeout that will expire before the test does so that
+ // we can terminate the subprocess with a more useful signal.
+
+ timeout := time.Until(td)
+
+ // If time allows, increase the termination grace period to 5% of the
+ // remaining time.
+ if gp := timeout / 20; gp > gracePeriod {
+ gracePeriod = gp
+ }
+
+ // When we run commands that execute subprocesses, we want to reserve two
+ // grace periods to clean up. We will send the first termination signal when
+ // the context expires, then wait one grace period for the process to
+ // produce whatever useful output it can (such as a stack trace). After the
+ // first grace period expires, we'll escalate to os.Kill, leaving the second
+ // grace period for the test function to record its output before the test
+ // process itself terminates.
+ timeout -= 2 * gracePeriod
+
+ ctx, cancel = context.WithTimeout(ctx, timeout)
+ t.Cleanup(cancel)
+ }
+ }
+ }
+
+ cmd := exec.CommandContext(ctx, name, args...)
+ cmd.Cancel = func() error {
+ if cancel != 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 cancel != nil {
+ cancel()
+ }
+ 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...)
+}
+
// CPUIsSlow reports whether the CPU running the test is suspected to be slow.
func CPUIsSlow() bool {
switch runtime.GOARCH {