xethya-extension-base/src/extension.js

import { Mixin } from 'lodash-decorators';

const Testeable = {
  isTesteable() {
    return true;
  }
}

@Mixin(Testeable)
export class Extension {
  constructor() {
    this._internal = true;
  }

  isInternal() {
    return this._internal;
  }
}