standardized-audio-context-mock

A mocked version of the standardized-audio-context module.

This library is meant to test code which is using standardized-audio-context without actually rendering any audio.

Usage

standardized-audio-context-mock is published on npm and can be installed as usual.

npm install standardized-audio-context-mock

Testing

Let's say you have the following code that you want to test:

// File `./play.ts`
import { IAudioBuffer, IAudioContext } from 'standardized-audio-context';

export const play = (audioBuffer: IAudioBuffer, audioContext: IAudioContext) => {
    const audioBufferSourceNode = audioContext.createBufferSource();

    audioBufferSourceNode.buffer = audioBuffer;
    audioBufferSourceNode.connect(audioContext.destination);

    audioBufferSourceNode.start();
};

A test suite for the play() function which will run with Mocha and Chai and uses standardized-audio-context-mock might look like this:

// File `./play.test.js`
import { AudioBuffer, AudioContext, registrar } from 'standardized-audio-context-mock';
import { play } from './play';

describe('play()', () => {
    let audioBufferMock;
    let audioContextMock;

    afterEach(() => registrar.reset());

    beforeEach(() => {
        audioBufferMock = new AudioBuffer({ length: 10, sampleRate: 44100 });
        audioContextMock = new AudioContext();
    });

    it('should create a new AudioBufferSourceNode', () => {
        play(audioBufferMock, audioContextMock);

        expect(registrar.getAudioNodes(audioContextMock, 'AudioBufferSourceNode')).to.have.a.lengthOf(1);
    });

    it('should set the buffer property of the AudioBufferSourceNode', () => {
        play(audioBufferMock, audioContextMock);

        const [audioBufferSourceNodeMock] = registrar.getAudioNodes(audioContextMock, 'AudioBufferSourceNode');

        expect(audioBufferSourceNodeMock.buffer).to.equal(audioBufferMock);
    });

    it('should connect the AudioBufferSourceNode to destination', () => {
        play(audioBufferMock, audioContextMock);

        const [audioBufferSourceNodeMock] = registrar.getAudioNodes(audioContextMock, 'AudioBufferSourceNode');

        expect(audioBufferSourceNodeMock.connect).to.have.been.calledOnce;
        expect(audioBufferSourceNodeMock.connect).to.have.been.calledWithExactly(audioContextMock.destination);
    });

    it('should start the AudioBufferSourceNode', () => {
        play(audioBufferMock, audioContextMock);

        const [audioBufferSourceNodeMock] = registrar.getAudioNodes(audioContextMock, 'AudioBufferSourceNode');

        expect(audioBufferSourceNodeMock.start).to.have.been.calledOnce;
    });
});

Mocking

By default this library is not using any specific mocking library anymore. (Earlier versions only worked with Sinon.JS.)

However it is possible to provide any third party mocking implementation. You can use setMockingImplementation() for doing that. resetMockingImplementation() is restoring the default behavior.

Example: using Sinon.JS

If you want to use Sinon.JS (like older versions of this package provided automatically), you can configure it like this:

import { setMockingImplementation, resetMockingImplementation } from 'standardized-audio-context-mock';
import { stub } from 'sinon';

// provide the mocking implementation
setMockingImplementation((defaultImplementation) => stub().callsFake(defaultImplementation));

// run your tests

// reset the mocking implementation
resetMockingImplementation();

Example: using Vitest

It is for example also possible to use Vitest’s vi.fn() instead:

import { setMockingImplementation, resetMockingImplementation } from 'standardized-audio-context-mock';
import { vi } from 'vitest';

// provide the mocking implementation
setMockingImplementation((defaultImplementation) => vi.fn().mockImplementation(defaultImplementation));

// run your tests

// reset the mocking implementation
resetMockingImplementation();