Sinon.spy fails with imported method

Question

I have of couple JS modules, let's say A and B. In module A, I have a method which depends on another method imported from module B. Now how do I test with sinon.spy, whether the method from A triggers the method from B?

//ModuleA.js
import{ methodFromB } from "ModuleB.js";

function methodFromA (){
methodFromB();
}

export{
 methodFromA
}

//ModuleB.js
function methodFromB (){ 
 //doSomething
}

ModuleA.Spec.js

import sinon from 'sinon';
import { assert,expect } from "chai";
import * as modB from "ModuleB.js";

import { methodA } from '../js/ModuleA.js';


describe("ModuleA.js", function() {

beforeEach(function() {
    stubmethod = sinon.stub(modB, "methodB").returns("success");              
});

after(function() {

});

describe("#methodA", function() {
    it("Should call the method methodB", function() {
        expect(methodA()).to.deep.equal('success');
        expect(stubmethod.calledOnce).to.equal(true);
    });

});

});

After trying to stub methodB, i get the error "expected undefined to deeply equal 'success'".

Thanks in advance.

score 0 · Answer 1 · answered Aug 02 '18 at 05:03

0

you should mock module B, and expect it to.have.been.called instead of spy from methodFromA

answered Aug 02 '18 at 05:03

Vu Luu

792
5
16

I tried subbing methodB, But i am running into the error "expected undefined to deeply equal 'success'". – Murali Nepalli Aug 02 '18 at 06:22

score 0 · Answer 2 · answered Aug 04 '18 at 09:31

0

You stub the wrong function from module B. It is supposed to be methodFromB not methodB based on your source file.

describe("ModuleA.js", function () {

  beforeEach(function () {
    stubmethod = sinon.stub(modB, "methodFromB").returns("success"); // change to methodFromB
  });

  after(function () {
    stubmethod.restore(); // don't forget to restore
  });

  describe("#methodA", function () {
    it("Should call the method methodB", function () {
      expect(methodA()).to.deep.equal('success');
      expect(stubmethod.calledOnce).to.equal(true);
    });

  });
});

answered Aug 04 '18 at 09:31

deerawan

8,002
5
42
51

Thank you. I think i found the root cause. – Murali Nepalli Aug 17 '18 at 06:01
@MuraliNepalli what is the cause? – deerawan Aug 17 '18 at 06:02
@deerwan I corrected the typo you pointed out but the actual reason was "methodFromB" in module B does not have a return value. Hence I could not sub it with return value "success". if method has return value let' say "return ""something", then my stub would have worked. – Murali Nepalli Aug 17 '18 at 06:09
@MuraliNepalli glad that the real issue is found – deerawan Aug 17 '18 at 23:43

Sinon.spy fails with imported method

ModuleA.Spec.js

2 Answers2