Image-diff tests for the headless render path — the GPU-free Skia pipeline (init_headless + render_shape_raster) that powers server-side export. They're the Playwright-snapshot equivalent for code that runs with no browser/WebGL: boot the built WASM in Node, render a scene to PNG, and compare against a committed baseline with pixelmatch.

Running

./build                       # produce frontend/resources/public/js/render-wasm.*
pnpm install                  # one-time, pulls pngjs + pixelmatch
pnpm test:headless            # diff against baselines in __snapshots__/
pnpm test:headless:update     # (re)generate baselines, then review + commit them

A failing case writes __snapshots__/<name>.diff.png highlighting the changed pixels. Baselines are produced by CPU Skia, so they're deterministic across machines.

Scenes

Scenes are built through the WASM FFI in scenes.mjs (no .penpot file needed), so the suite is self-contained on this branch. Rendering real files headless needs the shape-tree serialization that lives in the exporter; once that's exposed as a JS module it can feed renderToPng through this same harness.

harness.mjs — load/boot the headless module, build fills, render to PNG, snapshot compare.
scenes.mjs — FFI scene builders.
*.test.mjs — node:test cases.
__snapshots__/ — committed baseline PNGs.