Sinon Class Constructor - node.js

Question

I have an Animal class as follows
Animal.js
export default class Animal {
constructor(type) {
this.type = type
}
getAnimalSound(animal) {
if (animal && animal.type == 'dog') return 'woof'
if (animal && animal.type == 'cat') return 'meow'
}
}
I make a zoo module which has a method for getAnimalSound() as follows
zoo.js
import Animal from './Animal'
export default function getAnimalSound(type) {
let animal = new Animal(type)
let animalSound = animal.getAnimalSound(animal)
return animalSound
}
Now how do i make unit testing for zoo module?
zoo.test.js
import sinon from 'sinon'
import Animal from './Animal'
import getAnimalSound from './zoo'
let animalStub = sinon.createStubInstance(Animal)
let a = animalStub.getAnimalSound.returns('woof')
let sound = getAnimalSound('cat')
console.log(sound)
So the problem is that the 'new' has no effect by the way i have stubbed in test.js
Can i achieve this?
Regards
Bobu P

Answer 1

You could use Link Seams to mock your ./animal.js module and Animal class.
E.g.
animal.ts:
export default class Animal {
type: any;
constructor(type) {
this.type = type;
}
getAnimalSound(animal) {
if (animal && animal.type == 'dog') return 'woof';
if (animal && animal.type == 'cat') return 'meow';
}
}
zoo.ts:
import Animal from './animal';
export default function getAnimalSound(type) {
let animal = new Animal(type);
let animalSound = animal.getAnimalSound(animal);
return animalSound;
}
zoo.test.ts:
import sinon from 'sinon';
import proxyquire from 'proxyquire';
import { expect } from 'chai';
describe('61716637', () => {
it('should pass', () => {
const animalInstanceStub = {
getAnimalSound: sinon.stub().returns('stubbed value'),
};
const AnimalStub = sinon.stub().returns(animalInstanceStub);
const getAnimalSound = proxyquire('./zoo', {
'./animal': { default: AnimalStub },
}).default;
const actual = getAnimalSound('bird');
expect(actual).to.be.equal('stubbed value');
sinon.assert.calledWith(AnimalStub, 'bird');
sinon.assert.calledWith(animalInstanceStub.getAnimalSound, animalInstanceStub);
});
});
unit test results with coverage report:
61716637
✓ should pass (2242ms)
1 passing (2s)
-----------|---------|----------|---------|---------|-------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
-----------|---------|----------|---------|---------|-------------------
All files | 54.55 | 0 | 33.33 | 66.67 |
animal.ts | 16.67 | 0 | 0 | 25 | 4-8
zoo.ts | 100 | 100 | 100 | 100 |
-----------|---------|----------|---------|---------|-------------------