init-if-needed.ts

private _initIfNeeded() {
    if (this._instantiated) {
      return;
    }
    if (!this._moduleFactory) {
      try {
        const moduleType = this._createCompilerAndModule();
        this._moduleFactory =
this._compiler.compileModuleAndAllComponentsSync(moduleType).ngModuleFactory;
      } catch (e) {
        const errorCompType = this._compiler.getComponentFromError(e);
        if (errorCompType) {
          throw new Error(
              `This test module uses the component ${stringify(errorCompType)} which is using a "templateUrl" or "styleUrls", but they were never compiled. ` +
              `Please call "TestBed.compileComponents" before your test.`);
        } else {
          throw e;
        }
      }
    }
    for (const {component, templateOf} of this._templateOverrides) {
      const compFactory = this._compiler.getComponentFactory(templateOf);
      overrideComponentView(component, compFactory);
    }
    const ngZone = new NgZone({enableLongStackTrace: true});
    const providers: StaticProvider[] = [{provide: NgZone, 
useValue: ngZone}];
    const ngZoneInjector = Injector.create({
      providers: providers,
      parent: this.platform.injector,
      name: this._moduleFactory.moduleType.name
    });
    this._moduleRef = this._moduleFactory.create(ngZoneInjector);
    (this._moduleRef.injector.get(ApplicationInitStatus) as any).runInitializers();
    this._instantiated = true;
 }