def METHOD_NAME(
    statlist,
    use,
    var_name,
    pref_attr,
    sort_by_largest,
    fill_missing_nan,
    add_meta_keys,
    num,
    tst,
    mean,
):
    stats = [x.copy() for x in statlist[use]]
    stat = helpers.merge_station_data(
        stats, var_name, pref_attr, sort_by_largest, fill_missing_nan, add_meta_keys
    )
    assert isinstance(stat, StationData)
    vardata = stat[var_name]
    assert len(vardata) == num
    assert stat.get_var_ts_type(var_name) == tst
    assert np.mean(vardata) == pytest.approx(mean, rel=1e-2)