threejs-imageloader-mock

Enables to mock/intercept image downloading with THREE.ImageLoader on node/mocha.

It enables to:

• mock image downloading by THREE.ImageLoader and its related components as THREE.TextureLoader etc, injecting mock class instead of image object.
• invoke error artificially on image loading.

Motivation

Since THREE.ImageLoader makes use of lazy loading feature of <img> tag, in other words since it does not depend on XMLHttpRequest, its loading cannot be intercepted by usual tools like nock. This module enables to intercept image downloading by overriding document.createElementNS().

Installation

Requires node.

npm i -D threejs-imageloader-mock

Usage

First require the module, then call success() or fail() method (usually in before clause).

const THREE = require('three');
const imgMock = require('threejs-imageloader-mock');
const assert = require('assert');

describe('App test', () => {

  it('Can mock image loading', ( done ) => {
    imgMock.success();
    const onLoad = ( texture ) => {
      console.log(texture); // Prints Mock object
      assert.equal(texture.src, 'http://0.0.0.0/foo/bar');
      assert.equal(texture.constructor.name, 'ImageElementMock');
      done();
    };
    // Without mock, this line results timeout.
    new THREE.ImageLoader().load('http://0.0.0.0/foo/bar', onLoad);
  });

  it('Can intercept with error', ( done ) => {
    imgMock.fail();
    const onLoad = () => {
      assert.fail();
    };
    const onError = ( error ) => {
      console.log(error); // THREE.ImageLoader will call onError callback.
      done();
    };
    // You must specify onError callback.
    new THREE.ImageLoader().load('http://0.0.0.0/foo/bar', onLoad, null, onError);
  });

});

Behaviours

After "successful" loading, ImageElementMock object in THREE.Texture.map property, replacing <img> element.

ImageElementMock {
  trigger: 'load', // please ignore this property
  crossOrigin: 'anonymous',
  src: 'http://0.0.0.0/foo/bar'
}

src and crossOrigin property will be added by THREE.ImageLoader.load() method, which can be made use of test.

Warning

This module does not ensure valid function of your WebGL program. Please make sure that it can cause some problems.

License

MIT