from poly_updown.strategy import crypto_taker_fee, fair_up_probability


def test_crypto_taker_fee_peaks_near_half() -> None:
    assert round(crypto_taker_fee(0.5), 4) == 0.0175
    assert crypto_taker_fee(0.1) < crypto_taker_fee(0.5)


def test_fair_probability_moves_with_distance() -> None:
    base = fair_up_probability(
        current_price=100.0,
        price_to_beat=100.0,
        seconds_remaining=60.0,
        sigma_price_per_sqrt_second=1.0,
    )
    high = fair_up_probability(
        current_price=102.0,
        price_to_beat=100.0,
        seconds_remaining=60.0,
        sigma_price_per_sqrt_second=1.0,
    )
    low = fair_up_probability(
        current_price=98.0,
        price_to_beat=100.0,
        seconds_remaining=60.0,
        sigma_price_per_sqrt_second=1.0,
    )

    assert low < base < high