MockStreamTransport

MockStreamTransport is a test-friendly transport that replaces real network calls with an in-memory event emitter. Use it in unit and component tests to push values on demand and assert against your component's reactive state without a running server.

Complete test example

The pattern below covers the full lifecycle: configure the transport in TestBed, create the component, emit values, and assert signal state.

import { Component, inject } from '@angular/core';
import { TestBed } from '@angular/core/testing';
import {
  provideStreamResource,
  MockStreamTransport,
  streamResource,
} from '@cacheplane/stream-resource';
 
@Component({ template: '' })
class RepoComponent {
  readonly repo = streamResource<{ name: string }>({
    url: () => '/api/repos/42',
  });
}
 
describe('RepoComponent', () => {
  let transport: MockStreamTransport;
 
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [RepoComponent],
      providers: [provideStreamResource({ transport: MockStreamTransport })],
    });
    transport = TestBed.inject(MockStreamTransport);
  });
 
  it('reflects the streamed value', () => {
    const fixture = TestBed.createComponent(RepoComponent);
    fixture.detectChanges();
 
    // Push a value into the stream — synchronous, no fakeAsync needed
    transport.emit('/api/repos/42', { name: 'my-repo' });
    fixture.detectChanges();
 
    expect(fixture.componentInstance.repo.value()).toEqual({ name: 'my-repo' });
    expect(fixture.componentInstance.repo.status()).toBe('streaming');
  });
 
  it('surfaces errors through the error signal', () => {
    const fixture = TestBed.createComponent(RepoComponent);
    fixture.detectChanges();
 
    transport.error('/api/repos/42', new Error('not found'));
    fixture.detectChanges();
 
    expect(fixture.componentInstance.repo.status()).toBe('error');
    expect(fixture.componentInstance.repo.error()).toBeInstanceOf(Error);
  });
});

MockStreamTransport API

| Method | Description | |--------|-------------| | emit(url, value) | Pushes a single value into the stream at the given URL path. | | error(url, err) | Triggers an error on the stream at the given URL path. | | complete(url) | Closes the stream cleanly, as if the server sent the final event. |

Deterministic tests

Because MockStreamTransport is synchronous by default, you can emit values and assert state changes in the same test tick — no fakeAsync or tick required.