How to test Angular Pipe with abstract class constructor autowired by typescript?

I have a pipe that sanatises HTML as below:

import { Pipe, PipeTransform } from '@angular/core';
import { DomSanitizer } from '@angular/platform-browser';

@Pipe({
    name: 'sanitiseHtml'
})

export class SanitiseHtmlPipe implements PipeTransform {

constructor(private _sanitizer: DomSanitizer) {}

    transform(value: any): any {
      return this._sanitizer.bypassSecurityTrustHtml(value);
    }

}

I want to test it as below:

describe('Pipe: Sanatiser', () => {
    let pipe: SanitiseHtmlPipe;

    beforeEach(() => {
        pipe = new SanitiseHtmlPipe(new DomSanitizer());
    });

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

The DomSanatizer is an abstract class which is autowired by typescript by passing it into a constructor:

constructor(private _sanitizer: DomSanitizer) {}

Currently I get the typescript errror:

Cannot create an instance of the abstract class 'DomSanitizer'.

Does anyone know what typescript does when instantiating dependencies passed into a constructor in Angular? Or what the way to test something like this is?