Testing

Handles get their pipeline from the PIPELINE_FACTORY token, so a test provides a fake factory and never touches the network or WebAssembly. This is how the library's own suite runs, in jsdom under Vitest.

A fake factory

import { TestBed } from '@angular/core/testing';
import { PIPELINE_FACTORY, type PipelineFactory, type PipelineLike } from 'ngx-transformers';
import { SentimentComponent } from './sentiment.component';

function fakeFactory(output: unknown): PipelineFactory {
  return async () => {
    const pipe = (async () => output) as PipelineLike;
    pipe.dispose = async () => {};
    return pipe;
  };
}

describe('SentimentComponent', () => {
  it('shows the top label', async () => {
    TestBed.configureTestingModule({
      imports: [SentimentComponent],
      providers: [
        { provide: PIPELINE_FACTORY, useValue: fakeFactory([{ label: 'POSITIVE', score: 0.98 }]) },
      ],
    });
    const fixture = TestBed.createComponent(SentimentComponent);
    await fixture.componentInstance.analyze('great');
    fixture.detectChanges();
    expect(fixture.nativeElement.textContent).toContain('POSITIVE 98.0%');
  });
});

The factory receives (task, model, options). Record them to assert that a component asks for the right model, device or dtype. options.progress_callback is the function the handle passes for progress; call it with { status: 'progress', file: 'onnx/model_quantized.onnx', progress: 50, loaded: 1, total: 2 } to drive the progress signal.

Driving the lifecycle

To test the loading state, hold the factory's promise until the test releases it:

let release!: () => void;
const gate = new Promise<void>((resolve) => (release = resolve));
const factory: PipelineFactory = async () => {
  await gate;
  return (async () => []) as PipelineLike;
};

const handle = TestBed.runInInjectionContext(() => createTextClassifier());
const loading = handle.load();
expect(handle.status()).toBe('loading');
release();
await loading;
expect(handle.status()).toBe('ready');

A factory that throws puts the handle in the error state; the next load() retries.

Handles outside components

create*() needs an injection context. In a test, wrap the call: TestBed.runInInjectionContext(() => createTextEmbedder()). The handle is then disposed with the test injector, or call dispose() yourself.

Microphone

createMicRecorder({ getUserMedia, createRecorder }) accepts fakes for navigator.mediaDevices.getUserMedia() and new MediaRecorder(stream), so a dictation UI can be tested without a real microphone. The fake recorder implements start(), stop(), ondataavailable and onstop; emit a Blob from ondataavailable and then call onstop to resolve stop().

Audio decoding

decodeAudio() needs AudioContext, which jsdom does not provide. Either install a fake on globalThis whose decodeAudioData() returns { numberOfChannels, getChannelData }, or pass Float32Array samples to transcribe() in tests and skip decoding.

Real models

For an occasional end-to-end check, run the real pipeline in a browser test runner such as Playwright rather than in jsdom: Transformers.js needs WebAssembly, fetch and the Cache API, and the first run downloads the model.