trueskill/tests/TrueSkill/DrawMarginTest.php

<?php

declare(strict_types=1);

namespace DNW\Skills\Tests\TrueSkill;

use DNW\Skills\TrueSkill\DrawMargin;
use DNW\Skills\Numerics\BasicMath;
use DNW\Skills\Numerics\GaussianDistribution;
use PHPUnit\Framework\TestCase;
use PHPUnit\Framework\Attributes\CoversClass;
use PHPUnit\Framework\Attributes\UsesClass;

#[CoversClass(DrawMargin::class)]
#[UsesClass(BasicMath::class)]
#[UsesClass(GaussianDistribution::class)]
final class DrawMarginTest extends TestCase
{
    private const float ERROR_TOLERANCE = 0.000001;

    public function testGetDrawMarginFromDrawProbability(): void
    {
        $beta = 25.0 / 6.0;
        // The expected values were compared against Ralf Herbrich's implementation in F#
        $this->assertDrawMargin(0.10, $beta, 0.74046637542690541);
        $this->assertDrawMargin(0.25, $beta, 1.87760059883033);
        $this->assertDrawMargin(0.33, $beta, 2.5111010132487492);
    }

    private function assertDrawMargin(float $drawProbability, float $beta, float $expected): void
    {
        $actual = DrawMargin::getDrawMarginFromDrawProbability($drawProbability, $beta);
        $this->assertEqualsWithDelta($expected, $actual, self::ERROR_TOLERANCE);
    }
}