Testing Angular Service importing TypeScript model

With an Angular Service that leverages a TypeScript model module to add some functionality, how can you stub the models methods?

Below is a super simplistic example, how can the #aServiceMethod method be tested without running the actual MyModel constructor?

_models/my-model.ts

class MyModel {
  name: string;

  constructor(attrs?: object) {
    Object.assign(this, attrs);
    this.doSomeStuff();
  }

  prive doSomeStuff() {
    this.name = this.name.toLowerCase();
  }
}

_services/some-service.ts

import { MyModel } from '@models/index';

...

public aServiceMethod(attrs) {
  return new MyModel(attrs);
}