def METHOD_NAME(self):
    invalid_excluded_dates = [date(2021, 2, 3), date(2021, 2, 3)]
    invalid_backfill = Backfill(
        TEST_BACKFILL_1.entry_date,
        TEST_BACKFILL_1.start_date,
        TEST_BACKFILL_1.end_date,
        invalid_excluded_dates,
        TEST_BACKFILL_1.reason,
        TEST_BACKFILL_1.watchers,
        TEST_BACKFILL_1.status,
    )
    with pytest.raises(ValueError) as e:
        validate_excluded_dates(invalid_backfill)
    assert "duplicate excluded dates" in str(e.value)