def METHOD_NAME(self, open_mock):
    self.config['play']['command'] = 'echo'
    self.config['play']['relative_to'] = '/something'
    path = os.path.relpath(self.item.path, b'/something')
    playlist = path.decode('utf-8')
    self.run_and_assert(
        open_mock, expected_cmd='echo', expected_playlist=playlist)