trueskill-tt/tests/game.rs

use trueskill_tt::{
    ConstantDrift, ConvergenceOptions, Game, GameOptions, Gaussian, InferenceError, Outcome, Rating,
};

type R = Rating<i64, ConstantDrift>;

fn default_rating() -> R {
    R::new(
        Gaussian::from_ms(25.0, 25.0 / 3.0),
        25.0 / 6.0,
        ConstantDrift(25.0 / 300.0),
    )
}

#[test]
fn game_ranked_1v1_golden() {
    let a = default_rating();
    let b = default_rating();
    let g = Game::<i64, _>::ranked(
        &[&[a], &[b]],
        Outcome::winner(0, 2),
        &GameOptions::default(),
    )
    .unwrap();
    let p = g.posteriors();
    assert!(p[0][0].mu() > 25.0);
    assert!(p[1][0].mu() < 25.0);
    assert!((p[0][0].sigma() - p[1][0].sigma()).abs() < 1e-6);
}

#[test]
fn game_one_v_one_shortcut() {
    let a = default_rating();
    let b = default_rating();
    let (a_post, b_post) =
        Game::<i64, _>::one_v_one(&a, &b, Outcome::winner(0, 2), &GameOptions::default()).unwrap();
    assert!(a_post.mu() > 25.0);
    assert!(b_post.mu() < 25.0);
}

#[test]
fn game_ranked_rejects_bad_p_draw() {
    let a = R::new(Gaussian::default(), 1.0, ConstantDrift(0.0));
    let err = Game::<i64, _>::ranked(
        &[&[a], &[a]],
        Outcome::winner(0, 2),
        &GameOptions {
            p_draw: 1.5,
            score_sigma: 1.0,
            convergence: ConvergenceOptions::default(),
        },
    )
    .unwrap_err();
    assert!(matches!(err, InferenceError::InvalidProbability { .. }));
}

#[test]
fn game_ranked_rejects_mismatched_ranks() {
    let a = R::new(Gaussian::default(), 1.0, ConstantDrift(0.0));
    let err = Game::<i64, _>::ranked(
        &[&[a], &[a]],
        Outcome::ranking([0, 1, 2]),
        &GameOptions::default(),
    )
    .unwrap_err();
    assert!(matches!(err, InferenceError::MismatchedShape { .. }));
}

#[test]
fn game_free_for_all_three_players() {
    let a = default_rating();
    let b = default_rating();
    let c = default_rating();
    let g = Game::<i64, _>::free_for_all(
        &[&a, &b, &c],
        Outcome::ranking([0, 1, 2]),
        &GameOptions::default(),
    )
    .unwrap();
    let p = g.posteriors();
    assert_eq!(p.len(), 3);
    assert!(p[0][0].mu() > p[1][0].mu());
    assert!(p[1][0].mu() > p[2][0].mu());
}

#[test]
fn game_log_evidence_is_finite() {
    let a = default_rating();
    let b = default_rating();
    let g = Game::<i64, _>::ranked(
        &[&[a], &[b]],
        Outcome::winner(0, 2),
        &GameOptions::default(),
    )
    .unwrap();
    assert!(g.log_evidence().is_finite());
    assert!(g.log_evidence() < 0.0);
}

/// `one_v_one` used to hardcode `GameOptions::default()`, so a 1v1 could
/// never set `p_draw` and a drawn 1v1 was unreachable through it.
#[test]
fn one_v_one_honours_the_draw_probability_it_is_given() {
    let a = default_rating();
    let b = default_rating();

    // Default options still reject a draw, because the default p_draw is zero.
    let err = Game::<i64, _>::one_v_one(&a, &b, Outcome::draw(2), &GameOptions::default())
        .expect_err("a draw needs a positive p_draw");
    assert!(matches!(
        err,
        InferenceError::TieWithoutDrawProbability { .. }
    ));

    // With a draw probability supplied it succeeds — which was impossible
    // before the signature took options.
    let options = GameOptions {
        p_draw: 0.25,
        ..GameOptions::default()
    };
    let (a_post, b_post) = Game::<i64, _>::one_v_one(&a, &b, Outcome::draw(2), &options)
        .expect("a draw is representable once p_draw is positive");

    // A symmetric draw leaves the means alone and sharpens both sides.
    assert!((a_post.mu() - b_post.mu()).abs() < 1e-9);
    assert!(a_post.sigma() < 25.0 / 3.0);
}

/// Convergence options reach the 1v1 path too, not just `p_draw`.
#[test]
fn one_v_one_honours_convergence_options() {
    let a = default_rating();
    let b = default_rating();
    let options = GameOptions {
        convergence: ConvergenceOptions::default(),
        ..GameOptions::default()
    };
    let (a_post, _) = Game::<i64, _>::one_v_one(&a, &b, Outcome::winner(0, 2), &options).unwrap();
    assert!(a_post.mu() > 25.0);
}