mock the server response even the server is unreachable

Things I know (please correct me if I'm wrong, thank you :)):

HttpInterceptor works in a way similar to Aspect-oriented programming;
adding/modifying httpOptions can be achieved for requests;
modifying the response with clone() can also be achieved for response;

My problems

I want to test some libraries while their related servers can be down sometimes when developing I just care about the data no interaction with server is okay

Is it possible that I can just return a mock data already prepared without requesting the server when the request met some patterns even the service lies in other libraries?

My Requirements

all the logic in the libraries stays the same;
using the mock data to respond to the http request from the libraries;

Updated 2019-01-15

Thanks to the help of @Sachin Gupta, I tested the interceptor further with this demo.

What have been done:

auth-interceptor.ts to add headers for the request;
logging-interceptor.ts added to track the request details and time cost;
data-mocking-interceptor.ts to stop the request to the server and return the mock data directly.

Solution

Have a look at this.

https://stackblitz.com/edit/angular-json-http-response-catch

If the server is reachable, the data is populated, otherwise mocked is sent as response

Interceptor

export class NoopInterceptor implements HttpInterceptor {

  intercept(req: HttpRequest<any>, next: HttpHandler):
    Observable<HttpEvent<any>> {
      let response = new HttpResponse();
      response = response.clone({body: [{"sads":"ewre"}]});
   
    return next.handle(req).pipe(catchError((err) => {return of(response).pipe(delay(10))}) );
  }
}