如何在angular中测试以下异步函数？

import { fakeAsync, tick } from '@angular/core/testing';

it('should test async function', fakeAsync(() => {
  let result: any;
  asyncFunction().then(res => {
    result = res;
  });
  tick(); // 等待异步函数执行完毕
  expect(result).toBe(expectedResult);
}));

import { async, ComponentFixture, TestBed } from '@angular/core/testing';

it('should test async function', async(() => {
  let result: any;
  asyncFunction().then(res => {
    result = res;
  });
  fixture.whenStable().then(() => {
    expect(result).toBe(expectedResult);
  });
}));

import { asyncFunction } from './async-function';

it('should test async function', (done: DoneFn) => {
  let result: any;
  asyncFunction().then(res => {
    result = res;
    expect(result).toBe(expectedResult);
    done();
  });
});