@audio/assert

Audio assertions for CI. Measure and assert peak, RMS, silence, clipping, DC offset, duration, channels, sample rate, pitch, sample-wise regressions, and content hashes on any AudioBuffer-like object or raw Float32Array/number[] samples.

npm install @audio/assert

Use

Every function measures — and given an expectation it also asserts, throwing an Error with a precise message on failure and returning the measured value on success:

import { frequency, silent, unclipped, peak } from '@audio/assert'

frequency(buffer, 44100)          // → 440.01 (measured Hz)
frequency(buffer, 44100, 440)     // → 440.01, or throws "frequency 452.31 Hz (47.9 cents from 440 Hz)..."
silent(tail)                      // → 0.0000012, or throws "not silent: peak -52.1 dBFS..."
unclipped(mix)                    // → 0.98, or throws "clipping: channel 0, samples 812-819..."
peak(render, 0.25, 1e-2)          // → 0.249, or throws

Test runners

A thrown Error is a failing test everywhere, so there is no integration layer: the same call works verbatim under node:test, bun:test, Deno.test, tape, tap, ava, uvu, mocha, jasmine, jest, and vitest — or in a bare node script.js with no runner at all.

// node:test
import test from 'node:test'
import { frequency } from '@audio/assert'

test('oscillator renders 440 Hz', () => {
  frequency(buffer, ctx.sampleRate, 440)
})

// tape
import test from 'tape'
import { frequency } from '@audio/assert'

test('oscillator renders 440 Hz', t => {
  t.doesNotThrow(() => frequency(buffer, ctx.sampleRate, 440))
  t.end()
})

// ava
import test from 'ava'
import { frequency } from '@audio/assert'

test('oscillator renders 440 Hz', t => {
  t.notThrows(() => frequency(buffer, ctx.sampleRate, 440))
})

CI with web-audio-api

web-audio-api's OfflineAudioContext renders a real Web Audio graph to memory, no speaker or device required — pair it with @audio/assert for a full graph-in, assertion-out CI test:

import { OfflineAudioContext } from 'web-audio-api'
import { frequency, peak, unclipped, dc } from '@audio/assert'

let ctx = new OfflineAudioContext(1, 44100, 44100)
let osc = ctx.createOscillator()
osc.frequency.value = 440
osc.connect(ctx.destination)
osc.start()

let buffer = await ctx.startRendering()

frequency(buffer, ctx.sampleRate, 440)
unclipped(buffer)
dc(buffer, 0.01)
peak(buffer, 1, 1e-2)

API

Input is either an AudioBuffer-like object (numberOfChannels, sampleRate, length, duration, getChannelData(ch)) or a raw Float32Array/number[], treated as a single channel. Multi-channel measures that report one overall number (peak, rms, hash) pool all channels; measures where a location matters (unclipped, dc, matches) report the specific channel.

peak(input, expected?, tol=1e-4) → number

Absolute sample maximum.

rms(input, expected?, tol=1e-4) → number

sqrt(mean(x²)), the standard average-power measure (AES17 / IEC 61606).

silent(input, floorDb=-90) → number

Throws if any sample's peak level exceeds floorDb. -90 dBFS sits below 16-bit PCM's ~-96 dBFS theoretical noise floor with headroom for dither/render rounding.

audible(input, floorDb=-60) → number

Throws if the signal's RMS level is at or below floorDb — catches an accidentally muted or zeroed graph. -60 dBFS is well below normal program level (-20..-6 dBFS) but well above the silence floor.

unclipped(input, limit=1) → number

Throws on true clipping: 3+ consecutive samples at/above limit, not a single sample that legitimately grazes full scale. Reports the channel and sample range; returns the peak.

dc(input, maxDc?) → number

Worst per-channel sample mean; throws when a channel's |mean| exceeds maxDc (0.01 is a sensible gate — tight enough to catch a stuck offset, loose enough for render noise).

duration(buffer, seconds?, tol=1e-3) / channels(buffer, count?) / sampleRate(buffer, rate?)

Buffer-shape measures (require an AudioBuffer-like input); each asserts when the expectation is given.

frequency(input, sampleRate, hz?, tolCents=10) → number

Fundamental frequency via autocorrelation (with parabolic interpolation for sub-sample precision) — robust to harmonics and DC offset, unlike zero-crossing counting; the same principle as pitch trackers like YIN. Tolerance is in cents (100 cents = 1 semitone) so it stays musically meaningful across the frequency range.

matches(a, b, tol=1e-4) → number

Sample-wise comparison for golden-audio regression tests. Reports the first diverging channel/index; returns the max error.

hash(input, expected?) → string

Short deterministic content hash (FNV-1a) over samples quantized to 16-bit steps, so inaudible float noise between engines/platforms doesn't change the hash. Not cryptographic — for regression detection only.

License

MIT, ॐ