Angular - 为 switchMap 编写单元测试用例

Question

以下是我的两种服务方式

    getCountries(offset: number) {
          let url = this.configManagerService.countriesApiUrl;
          const httpHeaders = this.getHeaders();
          return this.httpClient.get(url + offset, { headers: httpHeaders });
        }
        
    getAllCountries(offset: number = 0, resultOld: any[] = []) {
      return this.getCountries(offset).pipe(
      
        //not getting covered
        switchMap((result: any) => {
          offset = result.length > 0 ? offset + result.length : -1;
          return offset >= 0
            ? this.getAllCountries(offset, [...resultOld, ...result])
            : of(resultOld);
        //not getting covered
        
        })
      );
    }

我能够编写涵盖getCountries 函数的单元测试用例，但无法理解如何涵盖我在cmets 之间提到的关于switchMap 的代码。试图用谷歌搜索，但找不到任何符合我要求的东西。这里的任何帮助将不胜感激。谢谢。

Answer 1

这里是一个案例的例子。

it('returns resultOld if result length is zero', (done: DoneFn) => {
  const resultOld = [];
  spyOn(service, 'getCountries').and.returnValue(of(resultOld));
  service.getAllCountries(2, resultOld).subscribe(results => {
    expect(results.length).toBe(0);
    done();
  });
});

it('calls getAllCountries over and over until converge', (done: DoneFn) => {
  const resultOld = [{ name: 'USA' }];
  spyOn(service, 'getCountries').and.returnValue(of(resultOld));
  service.getAllCountries(-1, resultOld).subscribe(results => {
    expect(results.length).toBe(1);
    done();
  });
});