The problem was I was declaring the TemplateStore as a provider in the component annotation. Just removed it and the test worked as expected.

@Component({
  selector: 'app-template-list-layout',
  standalone: true,
  providers: [/* REMOVED TEMPLATE STORE */],
  templateUrl: './template-list-layout.component.html',
  changeDetection: ChangeDetectionStrategy.OnPush,
})
export class TemplateListLayoutComponent {
  templateStore = inject(TemplateStore);