cancel := cancels[r.Intn(len(cancels))]
		cancel()
		select {
		case <-ctx.Done():
		default:
			errorf("ctx should be canceled")
		}
		checkValues("after cancel")
	}
}

func TestWithCancelCanceledParent(t *testing.T) {
	parent, pcancel := WithCancelCause(Background())
	cause := fmt.Errorf("Because!")
	pcancel(cause)

	c, _ := WithCancel(parent)
	select {
	case <-c.Done():
	default: