如何在Angular中创建一个模拟observable来测试http rxjs重试/重试？

// Start with an Observable.of() the initial request,and run the handler (which
// includes all interceptors) inside a concatMap(). This way,the handler runs
// inside an Observable chain,which causes interceptors to be re-run on every
// subscription (this also makes retries re-run the handler,including interceptors).
const events$: Observable<httpEvent<any>> =
    of (req).pipe(concatMap((req: httprequest<any>) => this.handler.handle(req)));

为了使请求可以重现,他们使用(req)启动它,因此我们可以在单元测试中模拟这种行为.例如：

spyOn(http,"get").and.returnValue(
    createRetriableStream(
       throwError("err"),throwError("err"),of("a")
    )
);

createRetriableStream函数可能看起来像这样：

function createRetriableStream(...resp$: any): any {
   let fetchData: Spy = createSpy("fetchData");
   fetchData.and.returnValues(...resp$);
   return of(undefined).pipe(switchMap((_) => fetchData()));
}

通常,重试逻辑与尝试之间的延迟一起使用,以覆盖此部分,您可以使用time progression syntax.因此您的测试可能如下所示：

it("throw error after 2 retries",() => {
        testscheduler.run(({ cold,expectObservable }) => {
            source$= createRetriableStream(cold("-#"),cold("-#"),cold("-3")).pipe(
                retryWhen(
                   return errors.pipe(
                       mergeMap((err) => {                
                           return 2 > repeatCount
                               ? throwError(err)
                               : timer(100,testscheduler);             
                       })
                  );)
             );
        expectObservable(source$).toBe("- 200ms --#");
  });