def METHOD_NAME(self):
    tb = FilesystemBackend(app=self.app, url=self.url)
    yesterday_task_ids = [uuid() for i in range(10)]
    today_task_ids = [uuid() for i in range(10)]
    for tid in yesterday_task_ids:
        tb.mark_as_done(tid, 42)
    day_length = 0.2
    time.sleep(day_length)  # let FS mark some difference in mtimes
    for tid in today_task_ids:
        tb.mark_as_done(tid, 42)
    with patch.object(tb, 'expires', 0):
        tb.cleanup()
    # test that zero expiration time prevents any cleanup
    filenames = set(os.listdir(tb.path))
    assert all(
        tb.get_key_for_task(tid) in filenames
        for tid in yesterday_task_ids + today_task_ids
    )
    # test that non-zero expiration time enables cleanup by file mtime
    with patch.object(tb, 'expires', day_length):
        tb.cleanup()
    filenames = set(os.listdir(tb.path))
    assert not any(
        tb.get_key_for_task(tid) in filenames
        for tid in yesterday_task_ids
    )
    assert all(
        tb.get_key_for_task(tid) in filenames
        for tid in today_task_ids
    )