如何在angular中测试http错误处理程序？

import { Injectable } from '@angular/core';
import { HttpClient, HttpErrorResponse } from '@angular/common/http';
import { throwError } from 'rxjs';
import { catchError } from 'rxjs/operators';

@Injectable()
export class HttpErrorService {
  constructor(private http: HttpClient) {}

  getData() {
    return this.http.get('https://api.example.com/data')
      .pipe(
        catchError(this.handleError)
      );
  }

  private handleError(error: HttpErrorResponse) {
    // 处理错误逻辑
    console.log('An error occurred:', error);
    return throwError('Something went wrong; please try again later.');
  }
}

import { TestBed, inject } from '@angular/core/testing';
import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
import { HttpErrorService } from './http-error.service';

describe('HttpErrorService', () => {
  let service: HttpErrorService;
  let httpMock: HttpTestingController;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [HttpClientTestingModule],
      providers: [HttpErrorService]
    });
    service = TestBed.inject(HttpErrorService);
    httpMock = TestBed.inject(HttpTestingController);
  });

  afterEach(() => {
    httpMock.verify();
  });

  it('should handle HTTP errors', () => {
    const errorMessage = 'Server error';

    service.getData().subscribe(
      data => fail('Expected an error, but received data'),
      error => {
        expect(error).toEqual('Something went wrong; please try again later.');
      }
    );

    const req = httpMock.expectOne('https://api.example.com/data');
    req.flush(errorMessage, { status: 500, statusText: 'Server Error' });
  });
});

ng test