def METHOD_NAME(self):
    fn = "changehc_covid_as_of_20200101.parquet"
    dropdate = datetime(2020, 1, 1)
    numtype = "covid"
    geo = "county"
    weekday = True
    dropdate = datetime(2020, 1, 1)        
    # Check when it cannot be stored
    store_backfill_file(combined_data, dropdate, backfill_dir, numtype, geo, weekday)
    assert fn not in os.listdir(backfill_dir)
    geo = "state"
    weekday = False
    dropdate = datetime(2020, 1, 1)        
    # Check when it cannot be stored
    store_backfill_file(combined_data, dropdate, backfill_dir, numtype, geo, weekday)
    assert fn not in os.listdir(backfill_dir)
    geo = "county"
    weekday = False
    dropdate = datetime(2020, 1, 1)        
    # Store backfill file
    store_backfill_file(combined_data, dropdate, backfill_dir, numtype, geo, weekday)
    assert fn in os.listdir(backfill_dir)
    fn = "changehc_covid_as_of_20200101.parquet"
    backfill_df = pd.read_parquet(backfill_dir + "/"+ fn, engine='pyarrow')
    selected_columns = ['time_value', 'fips', 'state_id',
                    'num', 'den', 'lag', 'issue_date']
    assert set(selected_columns) == set(backfill_df.columns)  
    os.remove(backfill_dir + "/" + fn)
    assert fn not in os.listdir(backfill_dir)