'Test the changing of the filename but not the folder name'

def test_fname_change(self):

    cache = self.init_cache()
    title = ((u'a' * 30) + u'bbb')
    cache.backend.PATH_LIMIT = 100
    cache.set_field(u'title', {3: title})
    cache.add_format(3, u'TXT', BytesIO('xxx'))
    cache.backend.PATH_LIMIT = 40
    cache.set_field(u'title', {3: title})
    fpath = cache.format_abspath(3, u'TXT')
    self.assertEqual(sorted([os.path.basename(fpath)]), sorted(os.listdir(os.path.dirname(fpath))))
