Estou seguindo o exemplo da aula mas me deparo com esse problema 
Property 'toMatchSnapshot' does not exist on type 'Matchers<CabecalhoComponent>
import { ComponentFixture, TestBed } from "@angular/core/testing";
import { CabecalhoComponent } from "./cabecalho.component";
describe('cabecalhoComponent', () => {
let component: CabecalhoComponent
let fixture: ComponentFixture<CabecalhoComponent>
beforeEach(() => {
TestBed.configureTestingModule({
imports: [CabecalhoComponent]
})
fixture = TestBed.createComponent(CabecalhoComponent)
component = fixture.componentInstance;
})
it('deveria rederizar a tela de acordo com as propriedade alt e src', () => {
component.alt = "https://exempllo.png"
component.src = 'exemplo'
expect(component).toMatchSnapshot()
})
})
