Angular 6 Unit testing: I want to stub a declared property for my test

I'm using angular version 6 and jasmine.

When I run ng test --sourceMap=false

Error I get is: videojs is not defined

I would like to stub videojs if possible.

My component that I'm testing:

import { AfterViewInit, Component } from '@angular/core';

declare const videojs: any;

@Component({
  selector: 'test-details',
  templateUrl: './test-details.component.html'
})
export class TestDetailsComponent implements AfterViewInit {
  public videoJSplayer: any;

  constructor() {}

  ngAfterViewInit(): void {
    this.initVideo();
  }

  public initVideo(): void {
    this.videoJSplayer = videojs(
      document.getElementById('video_player_id'),
      { controls: true, autoplay: false, preload: 'auto' }
    );
  }
}

My Unit test

import { async, ComponentFixture, TestBed } from '@angular/core/testing';
import { CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
import { TestDetailsComponent } from './test-details.component';

declare const videojs: any;

fdescribe('TestDetailsComponent', () => {
  let component: TestDetailsComponent;
  let fixture: ComponentFixture<TestDetailsComponent>;

  beforeEach(
    async(() => {
      TestBed.configureTestingModule({
        imports: [],
        declarations: [ TestDetailsComponent ],
        schemas: [ CUSTOM_ELEMENTS_SCHEMA ]
      }).compileComponents();
    })
  );

  beforeEach(() => {
    fixture = TestBed.createComponent(TestDetailsComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(true).toBeTruthy(true);
  });
});