trueskill-tt/tests/constructor_validation.rs

//! Every public entry point that takes a magnitude, in one place.
//!
//! This defect class was closed three times in one session and reopened twice,
//! because each fix validated the layer it had just touched and inferred the
//! rest: `HistoryBuilder` first, then `Game`'s own entry points, then the
//! constructors beneath both. A per-site fix cannot notice the site nobody
//! thought of.
//!
//! So this enumerates them. `sigma`, `beta` and `gamma` all enter inference
//! only as squares, which means a negative value does not fail — it behaves as
//! its absolute value, bit for bit, and the sign vanishes with no diagnostic.
//! Non-finite values poison every posterior derived from them.
//!
//! Adding a public constructor that takes one of these and not adding it here
//! is the failure this file exists to make harder.

use std::panic::{AssertUnwindSafe, catch_unwind};

use trueskill_tt::{ConstantDrift, Gaussian, History, Member, Outcome, Rating};

/// Did the entry point refuse the value, by panic or by `Err`?
fn refuses(f: impl FnOnce() -> bool) -> bool {
    catch_unwind(AssertUnwindSafe(f)).unwrap_or(true)
}

/// One entry point, as a name and a closure that applies a value to it.
type Case = (&'static str, Box<dyn Fn(f64) -> bool>);

/// Entry points that must reject a negative magnitude.
///
/// Each closure returns `true` if it refused by returning an error; a panic is
/// also a refusal and is caught.
#[test]
fn every_magnitude_parameter_rejects_a_negative_value() {
    let cases: Vec<Case> = vec![
        (
            "Gaussian::from_ms(sigma)",
            Box::new(|v| {
                let _ = Gaussian::from_ms(25.0, v);
                false
            }),
        ),
        (
            "Rating::new(beta)",
            Box::new(|v| {
                let _ = Rating::<i64, ConstantDrift>::new(
                    Gaussian::default(),
                    v,
                    ConstantDrift::new(0.0),
                );
                false
            }),
        ),
        (
            "ConstantDrift::new(gamma)",
            Box::new(|v| {
                let _ = ConstantDrift::new(v);
                false
            }),
        ),
        (
            "HistoryBuilder::sigma",
            Box::new(|v| {
                let _ = History::builder().sigma(v);
                false
            }),
        ),
        (
            "HistoryBuilder::beta",
            Box::new(|v| {
                let _ = History::builder().beta(v);
                false
            }),
        ),
        (
            "HistoryBuilder::score_sigma",
            Box::new(|v| {
                let _ = History::builder().score_sigma(v);
                false
            }),
        ),
        (
            "HistoryBuilder::p_draw",
            Box::new(|v| {
                let _ = History::builder().p_draw(v);
                false
            }),
        ),
        (
            "Member::with_drift_scale (at ingestion)",
            Box::new(|v| {
                let mut h = History::builder().build();
                h.add_events(vec![trueskill_tt::Event {
                    time: 1i64,
                    teams: smallvec::smallvec![
                        trueskill_tt::Team::with_members([Member::new("a").with_drift_scale(v)]),
                        trueskill_tt::Team::with_members([Member::new("b")]),
                    ],
                    outcome: Outcome::winner(0, 2),
                }])
                .is_err()
            }),
        ),
        (
            "Outcome::scores_with_noise (at ingestion)",
            Box::new(|v| {
                let mut h = History::builder().build();
                h.add_events(vec![trueskill_tt::Event {
                    time: 1i64,
                    teams: smallvec::smallvec![
                        trueskill_tt::Team::with_members([Member::new("a")]),
                        trueskill_tt::Team::with_members([Member::new("b")]),
                    ],
                    outcome: Outcome::scores_with_noise([3.0, 1.0], v),
                }])
                .is_err()
            }),
        ),
    ];

    let mut accepted = Vec::new();
    for (name, f) in &cases {
        if !refuses(|| f(-1.0)) {
            accepted.push(*name);
        }
    }

    assert!(
        accepted.is_empty(),
        "these accepted a negative magnitude, which is squared away silently \
         rather than honoured or refused:\n  {}",
        accepted.join("\n  ")
    );
}

/// Same set, for NaN and infinity.
///
/// `Gaussian::from_ms` is deliberately absent: a broken fit produces a NaN
/// sigma legitimately and `converge` reports it as `NonFiniteResult`. Rejecting
/// it in the constructor turned that reporting path into a panic inside
/// inference — see the comment on `from_ms`.
#[test]
fn every_magnitude_parameter_rejects_a_non_finite_value() {
    let cases: Vec<Case> = vec![
        (
            "Rating::new(beta)",
            Box::new(|v| {
                let _ = Rating::<i64, ConstantDrift>::new(
                    Gaussian::default(),
                    v,
                    ConstantDrift::new(0.0),
                );
                false
            }),
        ),
        (
            "ConstantDrift::new(gamma)",
            Box::new(|v| {
                let _ = ConstantDrift::new(v);
                false
            }),
        ),
        (
            "HistoryBuilder::sigma",
            Box::new(|v| {
                let _ = History::builder().sigma(v);
                false
            }),
        ),
        (
            "HistoryBuilder::beta",
            Box::new(|v| {
                let _ = History::builder().beta(v);
                false
            }),
        ),
        (
            "HistoryBuilder::mu",
            Box::new(|v| {
                let _ = History::builder().mu(v);
                false
            }),
        ),
        (
            "HistoryBuilder::score_sigma",
            Box::new(|v| {
                let _ = History::builder().score_sigma(v);
                false
            }),
        ),
        (
            "HistoryBuilder::p_draw",
            Box::new(|v| {
                let _ = History::builder().p_draw(v);
                false
            }),
        ),
    ];

    let mut accepted = Vec::new();
    for (name, f) in &cases {
        for bad in [f64::NAN, f64::INFINITY] {
            if !refuses(|| f(bad)) {
                accepted.push(format!("{name} accepted {bad}"));
            }
        }
    }

    assert!(
        accepted.is_empty(),
        "these accepted a non-finite magnitude:\n  {}",
        accepted.join("\n  ")
    );
}

/// The suite must not pass by refusing everything.
#[test]
fn ordinary_values_are_still_accepted() {
    let _ = Gaussian::from_ms(25.0, 8.33);
    let _ = Rating::<i64, ConstantDrift>::new(Gaussian::default(), 4.17, ConstantDrift::new(0.05));
    let _ = ConstantDrift::new(0.0833);
    let _ = History::builder()
        .mu(25.0)
        .sigma(8.33)
        .beta(4.17)
        .score_sigma(1.0)
        .p_draw(0.1);

    // Zero beta and zero gamma are legitimate, not degenerate.
    let _ = ConstantDrift::new(0.0);
    let _ = Rating::<i64, ConstantDrift>::new(Gaussian::default(), 0.0, ConstantDrift::new(0.0));
}