Wasm Worklet Smoke

WASM Worklet Smoke Test

Automated headless verification of an Emscripten + AudioWorklet build. Catches the class of failures that require a browser to surface: worklet registration failures, Emscripten runtime errors (self is not defined, fetch is not a function), WASM instantiation failures, and silent audio output.

Covers the gaps in a basic log-message-only smoke test: verifies actual audio output is non-silent, verifies the parameter message path, and catches all console.error / unhandled rejection events.

Requirements

• Node.js 18+ and npm
• Playwright with Chromium: npm install playwright && npx playwright install chromium
• Python 3 (for the HTTP server)
• make with a WASM build target (default: synth-wasm)
• Project setup: main.js must expose window.__audioCtx and window.__synthNode for audio verification (see Project Setup below)

Project setup

The audio verification step reads audioCtx and synthNode from window. The IIFE in main.js hides these by default. Add the following lines inside the IIFE after the AudioWorkletNode is connected and ready:

// Expose for automated testing (safe: AudioWorkletGlobalScope is isolated)
if (typeof window !== 'undefined') {
    window.__audioCtx  = audioCtx;
    window.__synthNode = synthNode;
}

Guard with window.__TEST_MODE if you prefer to enable this only during tests:

if (window.__TEST_MODE) {
    window.__audioCtx  = audioCtx;
    window.__synthNode = synthNode;
}

If the audio check is not needed, pass --no-audio-check to skip this step and the project setup requirement.

Instructions

Arguments are in $ARGUMENTS. Pass them directly to the smoke test script:

node "$(dirname "$0")/smoke.js" $ARGUMENTS

What the test verifies

| Check | What it catches | |-------|-----------------| | Build succeeds | Compilation errors in any source file, missing include paths | | Server starts | Broken asset copy, missing synth.js / synth.wasm | | WASM engine initialised log | Worklet registered, WASM instantiated, onRuntimeInitialized fired | | Zero console.error events | Any runtime JS error in the worklet or main thread | | Zero pageerror events | Uncaught exceptions | | Non-silent audio (AnalyserNode) | Silent engine (stuck envelope, null DSP output, broken computeSynth call) | | Expected fundamental frequency | Wrong oscillator frequency, detuning bug, wrong default param |

Options

| Option | Default | Description | |--------|---------|-------------| | --build-dir DIR | build/web | Directory containing synth.js and synth.wasm | | --port N | 8001 | Port for the local HTTP server | | --freq HZ | 440 | Expected fundamental frequency in Hz. Set to 0 to skip frequency check. | | --make-target TARGET | synth-wasm | Make target to build (skipped with --no-rebuild) | | --no-rebuild | off | Skip make , use existing build artifacts | | --no-audio-check | off | Skip AnalyserNode audio capture step | | --timeout MS | 15000 | Timeout waiting for engine initialisation | | --capture-delay MS | 200 | Delay after engine ready before capturing audio (allows envelope decay tail) |

Exit codes

• 0 — all checks passed
• 1 — build failed, engine did not initialise, console errors detected, or audio checks failed

Examples

# Standard run: build, serve, test
node smoke.js

# Skip rebuild (fast re-check after a CSS-only change)
node smoke.js --no-rebuild

# Different expected pitch, custom build dir
node smoke.js --freq 880 --build-dir dist/web

# Minimal check without audio verification
node smoke.js --no-audio-check

Adding to make

test-wasm: synth-wasm
	node tests/smoke_wasm.js --no-rebuild

Notes

• ENVIRONMENT=worker limitation: Emscripten has no audioworklet environment. ENVIRONMENT=worker is the closest option but still assumes self, self.location, and fetch() are available. These are absent in AudioWorkletGlobalScope. The known-working mitigation is a --pre-js polyfill for self/self.location and main-thread WASM compilation passed via processorOptions. This test will surface failures caused by missing polyfills.
• MODULARIZE=1 incompatibility: With MODULARIZE=1, --post-js content (including registerProcessor()) is wrapped inside the factory function and never executes at top level. This causes DOMException: AudioWorkletProcessor 'synth-processor' is not defined. This test catches that failure.
• Audio timing: The default capture delay of 200 ms assumes an envelope with ~10 ms attack, ~100 ms decay, ~300 ms release. Adjust --capture-delay if the synth's envelope shape differs significantly.
• Frequency resolution: At sampleRate=48000 and fftSize=2048, each FFT bin is ≈23.4 Hz wide. Frequency verification checks the peak bin and its two neighbours, so the tolerance is approximately ±1 bin (±23 Hz). For tight tuning verification use the audio-fft-sanity skill on a longer capture.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: gertsylvest
• Source: gertsylvest/meta-team
• License: MIT

Install and usage instructions live in the source repository linked above.