from datetime import date

import pytest

from payslip_ingest.tax_year import derive_tax_year


@pytest.mark.parametrize(
    ("pay_date", "expected"),
    [
        (date(2025, 4, 5), "2024/25"),
        (date(2025, 4, 6), "2025/26"),
        (date(2026, 4, 5), "2025/26"),
        (date(2026, 4, 6), "2026/27"),
        (date(2026, 12, 31), "2026/27"),
        (date(2027, 1, 1), "2026/27"),
        (date(2027, 4, 5), "2026/27"),
        (date(2027, 4, 6), "2027/28"),
    ],
)
def test_derive_tax_year(pay_date: date, expected: str) -> None:
    assert derive_tax_year(pay_date) == expected