Feature Request: Example how to test @defer -blocks

[GipHub123]

Hi, I'm not sure if this is a bug. I'm having trouble setting up a test case for a component with an @defer block using MockBuilder. Any insights?

@Component({
  selector: 'app-test',
  standalone: true,
  templateUrl: './test.component.html',
})
class TestComponent {
}

@defer (on viewport) {
  <div>text</div>
} @placeholder {
  <div>placeholder</div>
}

describe('TestComponent', () => {

  let fixture: ComponentFixture<TestComponent>;

  beforeEach(async () => {

    return MockBuilder(TestComponent)
      .beforeCompileComponents(testBed => {
        testBed.configureTestingModule({deferBlockBehavior: DeferBlockBehavior.Manual});
      });

  });

  beforeEach(async () => {

    fixture = TestBed.createComponent(TestComponent);

  });

  describe('template', () => {


    it('whenStable', async () => {

      await fixture.whenStable();

      const deferBlockFixtures: DeferBlockFixture[] = await fixture.getDeferBlocks();
      expect(deferBlockFixtures.length).toEqual(1);

    });

  });

});

Number of DeferBlockFixture seems always to be zero no matter How I set up the test case?

https://angular.dev/guide/templates/defer#testing-defer-blocks