Emberfall/tests/integration/step-10.18.test.js

// Step 10.18: Balance pass — assert Meadows level-1 win rate within 70–90% using fixed seed.
const { describe, it, before, after } = require('node:test');
const assert = require('node:assert/strict');
const { resolveCombat } = require('../../src/game/combat');
const { calcDerived } = require('../../src/game/stats');
const { getClass, getBaseStats } = require('../../src/game/classes');
const { mulberry32 } = require('../../src/utils/rng');
const { setup, teardown, cleanup } = require('../helpers');

// ─── Helpers ───────────────────────────────────────────────────────────────

/**
 * Simulate one hunt: hero vs a randomly-weighted monster from a zone.
 * Uses the same weighted-pick logic as huntService.
 */
function pickAndFight(zoneKey, classKey, rng) {
  const cls = getClass(classKey);
  const base = getBaseStats(classKey);
  const derived = calcDerived(base, 1, classKey);

  const hero = {
    class: classKey,
    level: 1,
    hpCurrent: derived.maxHp,
    str: base.str, agi: base.agi, int: base.int, vit: base.vit,
  };

  // Monster data from the DB (meadows monsters)
  const monsters = {
    meadows: [
      { name: 'Giant Rat', level: 1, hp: 55, attack: 15, defense: 5, speed: 10, weight: 30 },
      { name: 'Meadow Wolf', level: 2, hp: 85, attack: 22, defense: 9, speed: 14, weight: 20 },
      { name: 'Goblin Scrapper', level: 3, hp: 130, attack: 28, defense: 12, speed: 10, weight: 15 },
    ],
  };

  const zoneMonsters = monsters[zoneKey];
  const total = zoneMonsters.reduce((s, m) => s + m.weight, 0);
  let r = rng() * total;
  let monster = zoneMonsters[zoneMonsters.length - 1];
  for (const m of zoneMonsters) {
    r -= m.weight;
    if (r < 0) { monster = m; break; }
  }

  const fight = resolveCombat(hero, monster, rng);
  return fight.winner === 'hero';
}

// ─── Tests ─────────────────────────────────────────────────────────────────

describe('balance: Meadows level-1 win rate', () => {
  const rounds = 200;
  const SEED = 12345;

  it('Meadows level-1 win rate is between 70% and 90% for all classes', () => {
    let totalWins = 0;
    let totalFights = 0;

    for (let r = 0; r < rounds; r++) {
      for (const classKey of ['warrior', 'mage', 'ranger']) {
        const rng = mulberry32(SEED + r * 100 + ['warrior', 'mage', 'ranger'].indexOf(classKey));
        const won = pickAndFight('meadows', classKey, rng);
        if (won) totalWins++;
        totalFights++;
      }
    }

    const winRate = totalWins / totalFights;
    assert.ok(
      winRate >= 0.70 && winRate <= 0.90,
      `Meadows level-1 win rate is ${(winRate * 100).toFixed(2)}% (expected 70–90%)`
    );
  });

  it('Meadows level-1 win rate is consistent across different seeds', () => {
    // Run with 3 different seeds and check all are in range
    for (const seed of [42, 99, 7777]) {
      let totalWins = 0;
      let totalFights = 0;

      for (let r = 0; r < rounds; r++) {
        for (const classKey of ['warrior', 'mage', 'ranger']) {
          const rng = mulberry32(seed + r * 100 + ['warrior', 'mage', 'ranger'].indexOf(classKey));
          const won = pickAndFight('meadows', classKey, rng);
          if (won) totalWins++;
          totalFights++;
        }
      }

      const winRate = totalWins / totalFights;
      assert.ok(
        winRate >= 0.70 && winRate <= 0.90,
        `Seed ${seed}: Meadows level-1 win rate is ${(winRate * 100).toFixed(2)}% (expected 70–90%)`
      );
    }
  });
});

describe('balance: Crags level-1 win rate', () => {
  const rounds = 200;
  const SEED = 12345;

  it('Crags level-1 win rate is ≤ 15% for all classes', () => {
    let totalWins = 0;
    let totalFights = 0;

    const monsters = {
      crags: [
        { name: 'Ember Imp', level: 10, hp: 200, attack: 44, defense: 22, speed: 18, weight: 25 },
        { name: 'Stone Golem', level: 12, hp: 420, attack: 50, defense: 52, speed: 5, weight: 10 },
        { name: 'Ashfang Drake', level: 14, hp: 480, attack: 62, defense: 38, speed: 16, weight: 5 },
      ],
    };

    for (let r = 0; r < rounds; r++) {
      for (const classKey of ['warrior', 'mage', 'ranger']) {
        const rng = mulberry32(SEED + r * 100 + ['warrior', 'mage', 'ranger'].indexOf(classKey));

        const cls = getClass(classKey);
        const base = getBaseStats(classKey);
        const derived = calcDerived(base, 1, classKey);

        const hero = {
          class: classKey,
          level: 1,
          hpCurrent: derived.maxHp,
          str: base.str, agi: base.agi, int: base.int, vit: base.vit,
        };

        const zoneMonsters = monsters.crags;
        const total = zoneMonsters.reduce((s, m) => s + m.weight, 0);
        let cr = rng() * total;
        let monster = zoneMonsters[zoneMonsters.length - 1];
        for (const m of zoneMonsters) {
          cr -= m.weight;
          if (cr < 0) { monster = m; break; }
        }

        const fight = resolveCombat(hero, monster, rng);
        if (fight.winner === 'hero') totalWins++;
        totalFights++;
      }
    }

    const winRate = totalWins / totalFights;
    assert.ok(
      winRate <= 0.15,
      `Crags level-1 win rate is ${(winRate * 100).toFixed(2)}% (expected ≤ 15%)`
    );
  });
});