Process close does not wait for stdout/stderr to drain about child-process HOT 2 CLOSED

public function close()
{
    if (!$this->writable && !$this->closing) {
        return;
    }

    $this->closing = false;

    $this->readable = false;
    $this->writable = false;

    $this->emit('end', array($this));
    $this->emit('close', array($this));
    $this->loop->removeStream($this->stream);
    $this->buffer->removeAllListeners();

    // Check one last time for anything in the buffer
    if (is_resource($this->stream)) {

        $rest = stream_get_contents($this->stream);

        if ($rest !== '') {

            $this->emit('data', array($rest, $this));
        }
    }

    $this->removeAllListeners();

    $this->handleClose();
}

$loop = new \React\EventLoop\StreamSelectLoop();

$testString = 'x';

$process = new \React\ChildProcess\Process("echo $testString");

$stdOut = '';
$stdErr = '';

$process->on(
    'exit',
    function ($exitCode) use (&$stdOut, &$stdErr, $testString) {
        echo "exited\n";

        if ($exitCode) {
            throw new \Exception('Error running command');
        }

        if ($stdOut != $testString . "\n") {
            throw new \Exception('That is strange - output is ' . strlen($stdOut) . ' bytes');
        }
    }
);

$process->start($loop);

$process->stdout->on(
    'data',
    function ($output) use (&$stdOut) {
        echo ".";
        $stdOut .= $output;
    }
);
$process->stderr->on(
    'data',
    function ($output) use (&$stdErr) {
        echo "\nErr: --$output--\n";
        $stdErr .= $output;
    }
);

$loop->tick();
sleep(1); // comment this line out and it works fine

$loop->run();