playtester

name	playtester
description	Boots a generated Phaser game in headless Chromium (Playwright), drives input scenarios, captures canvas screenshots, diffs against baselines (pixelmatch), and emits a structured QA report with typed failures. Pure deterministic — no LLM. Use after codesmith writes Game.js, before refiner.

Playtester

Headless QA harness. Boots, drives, captures, diffs, asserts. Emits structured failures the refiner can act on.

When to use

After every codesmith / refiner write. Always before declaring a game complete.

Output contract — qa/qa-report.json

{
  "ts": "<ISO>",
  "url": "<dev server url>",
  "passed": <bool>,
  "scenarios": [
    {
      "scenario": "boot",
      "observations": { "blank": false, "fps": 60, "booted": true, "activeScenes": ["Game"], "gameState": {...} },
      "diff": { "status": "pass" | "fail" | "recorded", "ratio": <0..1>, "mismatched": <int> }
    }
  ],
  "failures": [
    { "scenario": "<name>", "kind": "<failure-kind>", "message": "<human-readable>" }
  ]
}

Failure kinds: boot-timeout, exception, console-error, screenshot-diff, low-fps, blank-canvas, no-movement, no-jump, scenario-crash.

Default scenarios

Name	Inputs	Asserts	Applies to
boot	(waits 60 frames)	Game scene active, fps ≥ 25, canvas non-blank, no errors	always
walk-right	hold ArrowRight 600ms	playerX delta > 0	always
walk-down	hold ArrowDown 600ms	playerY delta > 0	non-platformer
jump	press Space (held 50ms)	playerY drops then recovers	platformer
attack	press Space (held 50ms)	no exceptions	when GDD has attack/fire/shoot action

appliesTo(gdd) filter on each scenario picks the relevant subset for the genre.

Screenshot diff

• Engine: Playwright page.locator('canvas').screenshot() → pixelmatch
• Threshold: 0.1 YIQ delta per pixel; 5% pixel-ratio cap
• Baselines: qa/__baselines__/<scenario>.png. First run with no baseline → recorded (counts as pass).
• Update baselines: --update-baselines overwrites and returns recorded.

Process

1. Read game-state.json to get GDD (for scenario filtering).
2. Spawn dev server (vite) on a free port; wait for Local: http://... (ANSI-stripped).
3. Launch headless Chromium (system Chrome via channel: 'chrome', fallback to bundled).
4. goto(url). Wait for window.__gameReady === true && Game scene status === 5.
5. Focus canvas (Phaser keyboard target).
6. For each applicable scenario: register error listeners, run, snapshot, diff, run assertions.
7. Write qa/qa-report.json.
8. Append report to state.qa[] (keep last 5).
9. Kill dev server.
10. Exit code: 0 if passed, else 5.

Filtering noise

Console messages matching /Failed to load resource:.*404|favicon\.ico|\[vite\]/ are NOT counted as errors (browser noise unrelated to game logic).

Custom scenarios

To add a scenario, append to references/scenarios.md and register in the runner. Scenario shape:

{
  name: '<id>',
  description: '<one line>',
  appliesTo: (gdd) => bool,           // optional
  async run({ page, log }) {
    // do stuff with page.keyboard, page.mouse, page.evaluate
    return { observations: {...}, screenshot?: <Buffer> };
  }
}

VLM intent alignment pass

After the pixelmatch scenarios pass, run a second QA pass that uses Claude Haiku to judge whether the screenshot visually matches the original description:

node scripts/intent_qa.mjs <project-dir>
# Uses the boot scenario baseline screenshot by default.
# Requires ANTHROPIC_API_KEY in env.

Returns a score 0–10. Threshold: ≥ 6 = pass. Issues found by the VLM are appended to qa/qa-report.json as intent-mismatch failures for the refiner to act on.

The VLM checks: genre feel, player visibility, world rendering, entity presence. It does NOT check mechanics — only visual intent.

Integrate into the full pipeline:

node scripts/run_qa.mjs <project-dir> && node scripts/intent_qa.mjs <project-dir>

Scripts

• scripts/run_qa.mjs <project-dir> [--url URL] [--update-baselines] — the full runner.
• scripts/boot_check.mjs <project-dir> [--port N] — minimal smoke (just boot scenario).
• scripts/diff_one.mjs <baseline.png> <actual.png> [--out diff.png] — ad-hoc diff utility.
• scripts/intent_qa.mjs <project-dir> [--screenshot path] — VLM intent alignment pass.

References

• references/scenarios.md — full scenario catalog with code samples.
• references/baseline-workflow.md — when to update baselines, what's in them, gitignore conventions.
• references/known-noise.md — patterns of browser console noise we filter.

Dependencies

• playwright — browser automation (uses system Chrome via channel: 'chrome' to skip 170MB Chromium download).
• pixelmatch + pngjs — pure-JS diff.
• Generated game must have phaser + vite installed (handled by scripts/init_project.mjs).