def METHOD_NAME() -> None:
    """Test CachedStorage does flush to persistent storages.
    The CachedStorage flushes any modification of trials to a persistent storage immediately.
    """
    base_storage = RDBStorage("sqlite:///:memory:")
    storage = _CachedStorage(base_storage)
    study_id = storage.create_new_study(
        directions=[StudyDirection.MINIMIZE], study_name="test-study"
    )
    trial_id = storage.create_new_trial(study_id)
    trial = storage.get_trial(trial_id)
    with patch.object(base_storage, "set_trial_state_values", return_value=True) as set_mock:
        storage.set_trial_state_values(trial_id, state=trial.state, values=(0.3,))
        assert set_mock.call_count == 1
    trial_id = storage.create_new_trial(study_id)
    with patch.object(base_storage, "set_trial_param", return_value=True) as set_mock:
        storage.set_trial_param(
            trial_id, "paramA", 1.2, optuna.distributions.FloatDistribution(-0.2, 2.3)
        )
        assert set_mock.call_count == 1
    for state in [TrialState.COMPLETE, TrialState.PRUNED, TrialState.FAIL, TrialState.WAITING]:
        trial_id = storage.create_new_trial(study_id)
        with patch.object(base_storage, "set_trial_state_values", return_value=True) as set_mock:
            storage.set_trial_state_values(trial_id, state=state)
            assert set_mock.call_count == 1
    trial_id = storage.create_new_trial(study_id)
    with patch.object(base_storage, "set_trial_intermediate_value", return_value=None) as set_mock:
        storage.set_trial_intermediate_value(trial_id, 3, 0.3)
        assert set_mock.call_count == 1
    trial_id = storage.create_new_trial(study_id)
    with patch.object(base_storage, "set_trial_system_attr", return_value=None) as set_mock:
        storage.set_trial_system_attr(trial_id, "attrA", "foo")
        assert set_mock.call_count == 1
    trial_id = storage.create_new_trial(study_id)
    with patch.object(base_storage, "set_trial_user_attr", return_value=None) as set_mock:
        storage.set_trial_user_attr(trial_id, "attrB", "bar")
        assert set_mock.call_count == 1