angular - 测试 http 错误作为响应时，Jasmine 单元测试请求不会刷新

Question

我正在尝试使用 HttpTestingController 刷新带有 http 400 错误的响应。然而，它似乎永远不会被刷新，因为订阅的委托永远不会被调用。
记录请求对象的 _cancelled 属性表明返回 400 的 http 错误导致 _cancelled 属性设置为 true。我希望将错误响应传递给服务方法，以便可以测试它对 http 错误代码的处理。

考试：

  it('routes to error page when get roles receives an error', async(inject(
    [AgentManagementService, HttpTestingController],
    (service: AgentManagementService, backend: HttpTestingController) => {
      service.GetAgentPortalRoles().subscribe( (response) => {
        console.log(response);  // never gets called
        expect(1).toBe(1);
      });

      const request = backend.expectOne(environment.urlBase + 'v1/account/roles');
      expect(request.cancelled).toBeFalsy();
      console.log(request.cancelled); // is true
      request.flush( {}, { status: 400, statusText: 'Bad Request'});
      console.log(request.cancelled); // is false
    }
  )));

正在测试的服务中的功能：

  public GetAgentPortalRoles(): Observable<Array<string>> {
    return this.http.get<RolesResponse>(API_URL + 'v1/account/roles', { observe: 'response', headers })
      .pipe(
        map( response => {
          if (response.ok) {
            return response.body.roles;
          }
          this.router.navigateByUrl('/error');
          return null;
        }),
        catchError( () => {
          this.router.navigateByUrl('/error');
          return EMPTY;
        })
      );
  }