def _get_journalctl_output(self, mock_execute, lines=None, units=None): contents = b'Krusty Krab' mock_execute.return_value = (contents, '') data = utils.get_journalctl_output(lines=lines, units=units) cmd = ['journalctl', '--full', '--no-pager', '-b'] if lines is not None: cmd.extend(['-n', str(lines)]) if units is not None: [cmd.extend(['-u', u]) for u in units] mock_execute.assert_called_once_with(*cmd, binary=True, log_stdout=False) self.assertEqual(contents, data.read())