'Logged messages are written to ``logfile`` if ``--logfile`` is supplied
on the command line.'

def test_file_logging(self):

    logfile = FilePath(self.mktemp()).child('foo.log')
    logfile.parent().makedirs()
    d = self.run_script(EliotScript, options=['--logfile', logfile.path])
    d.addCallback(self._assert_logfile_messages, logfile=logfile)
    return d
