How to test a pipe with a dependency on the DomSanitizer abstract class?

Question

Angular

Good afternoon!
I'm new to writing unit tests, I'm trying to write a meaningful pipe test that allows html to be output in a
pipe template:

import { Pipe, PipeTransform } from '@angular/core';
import { DomSanitizer, SafeHtml, SafeStyle, SafeScript, SafeUrl, SafeResourceUrl } from '@angular/platform-browser';

@Pipe({
  name: 'safe'
})
export class SafePipe implements PipeTransform {

  constructor(protected sanitizer: DomSanitizer) {}

 public transform(value: any, type: string): SafeHtml | SafeStyle | SafeScript | SafeUrl | SafeResourceUrl {
    switch (type) {
      case 'html': return this.sanitizer.bypassSecurityTrustHtml(value);
      case 'style': return this.sanitizer.bypassSecurityTrustStyle(value);
      case 'script': return this.sanitizer.bypassSecurityTrustScript(value);
      case 'url': return this.sanitizer.bypassSecurityTrustUrl(value);
      case 'resourceUrl': return this.sanitizer.bypassSecurityTrustResourceUrl(value);
      default: throw new Error(`Invalid safe type specified: ${type}`);
    }
  }
}

spec:

import { SafePipe } from './safe.pipe';
import { TestBed } from '@angular/core/testing';
import { DomSanitizer,  SafeHtml, SafeStyle, SafeScript, SafeUrl, SafeResourceUrl} from '@angular/platform-browser';

describe('SafePipe', () => {
  let  sanitizer: DomSanitizer;
  let  pipe: SafePipe;

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [DomSanitizer]
    }).compileComponents();
    sanitizer = TestBed.get(DomSanitizer);
    pipe = new SafePipe(sanitizer);

  });

  it('create an instance', () => {
     expect(pipe).toBeTruthy();
  });

  it('it should return safe HTML', () => {
    const html = '<h1>Title</h1>';
    const safeHtml = pipe.transform(html, 'html');
    expect(pipe.transform(html, 'html')).toBe(html);
  });
});

I get the error: TypeError :
this.sanitizer.bypassSecurityTrustHtml is not a
function 9876/_karma_webpack_/webpack:/src/app/co... DomSanitazer abstract class First I wrote a simpler version of the test, with the same error:

import { SafePipe } from './safe.pipe';
import { TestBed } from '@angular/core/testing';
import { DomSanitizer,  SafeHtml, SafeStyle, SafeScript, SafeUrl, SafeResourceUrl} from '@angular/platform-browser';

describe('SafePipe', () => {
  let  sanitizer: DomSanitizer;
  const pipe = new SafePipe(sanitizer);

  it('create an instance', () => {
     expect(pipe).toBeTruthy();
  });

  it('it should return safe HTML', () => {
    const html = '<h1>Title</h1>';
    expect(pipe.transform(html,'html')).toBe(html);
  });
});

The question is how to test such pipe's