Mocha: Approach to Testing instance of express.Router

Question

I've been designing a javascript controller file and I want to testing if the instance of my controller have a instance of the express's method Router() .

import {expect} from 'chai';
import {UF_Controller} from '../../controllers/uf.controller.js';

describe('UF Controller', UFControllerDescription);

function UFControllerDescription(){
    it('1. Should be have a express router instance', spec1);

    function spec1(){
        expect(UF_Controller.router).itself.to.respondTo('get');
        expect(UF_Controller.router).itself.to.respondTo('post');
        expect(UF_Controller.router).itself.to.respondTo('put');
        expect(UF_Controller.router).itself.to.respondTo('delete');
    }
}

and my controller

import express from 'express';
import { uf } from '../models/uf.model';

class UFController{

    constructor(){
        this.router = express.Router();
        this.router.get('/', this.getAll);
  }

    getAll(req, res, next){
        res.json(uf.todayUF());
    }

    getUF(req, res, next){
    }

    insertUF(req, res, next){
    }

    replaceUF(req, res, next){
    }

    updateUF(req, res, next){
    }

    deleteUF(req, res, next){
    }
}

export const UF_Controller = new UFController();

My question is: This is a valid way check an instance of the express router???

Answer 1

There's no need to duck-type Express router.

express.Router isn't a constructor and doesn't establish normal prototype chain that can be detected with instanceof . Instead, it establishes prototype chain manually via hacky mixin technique .

It can be tested with

expect(Object.getPrototypeOf(UF_Controller.router)).to.equal(express.Router);