stack/tests/lead/test_params_money.py

"""lead.params carries the paper's printed parameters; lead.money rounds
dollar lines to the cent half away from zero."""

from __future__ import annotations

import pytest

from lead.money import cents
from lead.params import (
    ACPT_GUARDRAILS,
    BASE_YEAR_ALIGNMENT_MINIMUMS,
    BASE_YEAR_WEIGHTS,
    DISCOUNT_RATES,
    QUALITY_WITHHOLD_RATE,
    RETENTION_INCENTIVE_RATE,
    RISK_CORRIDORS,
    RISK_SCORE_GROWTH_CAPS,
    SEQUESTRATION_RATE,
    model_year,
)


def test_settlement_rates():
    assert (QUALITY_WITHHOLD_RATE, RETENTION_INCENTIVE_RATE, SEQUESTRATION_RATE) == (
        0.03,
        0.02,
        0.02,
    )


def test_tables_5_4_1_and_5_4_3_risk_corridors():
    def table(option, scenario):
        return [(c.lower, c.upper, c.rate) for c in RISK_CORRIDORS[(option, scenario)]]

    for scenario in ("savings", "losses"):
        assert table("Global", scenario) == [
            (0.0, 0.15, 1.00),
            (0.15, 0.35, 0.50),
            (0.35, 0.50, 0.25),
            (0.50, None, 0.10),
        ]
    assert table("Professional", "savings")[0] == (0.0, 0.10, 0.60)
    assert table("Professional", "losses")[0] == (0.0, 0.10, 0.50)
    assert (
        table("Professional", "losses")[1:]
        == table("Professional", "savings")[1:]
        == [
            (0.10, 0.15, 0.35),
            (0.15, 0.20, 0.15),
            (0.20, None, 0.05),
        ]
    )


def test_table_3_5_1_acpt_guardrails():
    assert ACPT_GUARDRAILS[1] == (-0.002, 0.003)
    assert ACPT_GUARDRAILS[4] == (-0.008, 0.012)
    assert {ACPT_GUARDRAILS[y] for y in range(5, 11)} == {(-0.010, 0.015)}


def test_benchmark_parameters():
    assert dict(RISK_SCORE_GROWTH_CAPS) == {
        "A&D": 0.03,
        "ESRD": 0.03,
        "High Needs": 0.04,
    }
    assert dict(BASE_YEAR_WEIGHTS["Newly Entering"]) == {
        "BY1": 0.1,
        "BY2": 0.3,
        "BY3": 0.6,
    }
    assert sum(BASE_YEAR_WEIGHTS["Renewing"].values()) == pytest.approx(1.0)
    assert BASE_YEAR_ALIGNMENT_MINIMUMS["newly_entering"][:5] == (
        600,
        1200,
        1800,
        2400,
        3000,
    )
    assert BASE_YEAR_ALIGNMENT_MINIMUMS["high_needs_esrd"][9] == 1000


def test_parameters_are_read_only():
    with pytest.raises(TypeError):
        DISCOUNT_RATES["Lower-spending"][2027] = 0.0  # type: ignore[index]


def test_model_year():
    assert (model_year(2027), model_year(2036)) == (1, 10)
    with pytest.raises(ValueError, match="outside the LEAD model"):
        model_year(2037)


@pytest.mark.parametrize(
    "amount,expected",
    [
        (184_593.6544, 184_593.65),
        (164_756.19264, 164_756.19),
        (2_948_334.2768, 2_948_334.28),
        (0.125, 0.13),  # half away from zero, not half to even
        (-0.125, -0.13),
        (2.5, 2.5),
        (-0.001, 0.0),
        (0.0, 0.0),
        (1_877_213.43, 1_877_213.43),
    ],
)
def test_cents(amount, expected):
    assert cents(amount) == expected


def test_cents_never_returns_negative_zero():
    assert str(cents(-0.001)) == "0.0"