Clearing all pending tasks from the fake async zone

component.spec.ts

import { fakeAsync, tick } from '@angular/core/testing';
import { discardFakeAsyncTimers ) from './helpers';

const myComponent = {};

describe('My Component', () => {
  before(fakeAsync(() => {
    myComponent.getAsyncData();
    
    // Run async stuff.

    tick();

    // Uh oh, some code we don't control keeps adding async tasks!

    discardFakeAsyncTimers();

    // Gone now.
  }));

  it('should work', () => {
    expect(myComponent.asyncResult).toBe('correct');
  });
});

helpers.ts

import 'zone.js';

export function discardFakeAsyncTimers() {
  const fakeZoneSpec = Zone.current.get('FakeAsyncTestZoneSpec');
  fakeZoneSpec.pendingPeriodicTimers.length = 0;
  fakeZoneSpec.pendingTimers.length = 0;
}