How to mock nested dependencies in NodeJS

Question

I have a Module a

const b = require(./b);

function aGetResult() {
  return b.getInfo();
}

Module B

const c = require(./c);
    
function getInfo() {
  return getDetailInfo();
}

function getDetailInfo() {
    const result = c.getApiResult();
    return result
}

Module C

function getApiResult() {
  return api.get(/test/1);
}

I've written a test for module A but am running into an issue with stubbing dependencies.I just want to stub c.getApiResult() and not b.getInfo() or b.getDetailInfo(). I've tried selectively stubbing using proxyquire but am having issues. Any help?

You want to test module a and stub module c?

Lin Du
– Lin Du

2020-08-06 04:19:42 +00:00
Commented Aug 6, 2020 at 4:19 — Lin Du
– Lin Du, Commented Aug 6, 2020 at 4:19
Yes, technically not a unit test

jbs87
– jbs87

2020-08-06 14:55:09 +00:00
Commented Aug 6, 2020 at 14:55 — jbs87
– jbs87, Commented Aug 6, 2020 at 14:55

Lin Du · Accepted Answer · 2020-12-23 07:10:41Z

You should use Globally override require of proxyquire package.

a depends b, b depends on c. Now you want to mock the indirect c dependency instead of direct b dependency when you test a. It's NOT recommended to do this. But anyway, here is the solution:

E.g.

a.js:

const b = require('./b');

function aGetResult() {
  return b.getInfo();
}

exports.aGetResult = aGetResult;

b.js:

const c = require('./c');

function getInfo() {
  return getDetailInfo();
}

function getDetailInfo() {
  const result = c.getApiResult();
  return result;
}

module.exports = { getInfo };

c.js:

const api = {
  get(url) {
    return 'real result';
  },
};

function getApiResult() {
  return api.get('/test/1');
}

module.exports = { getApiResult };

a.test.js:

const proxyquire = require('proxyquire');
const { expect } = require('chai');
const sinon = require('sinon');

describe('63275147', () => {
  it('should pass', () => {
    const stubs = {
      './c': {
        getApiResult: sinon.stub().returns('stubbed result'),
        '@global': true,
      },
    };
    const a = proxyquire('./a', stubs);
    const actual = a.aGetResult();
    expect(actual).to.be.eq('stubbed result');
    sinon.assert.calledOnce(stubs['./c'].getApiResult);
  });
});

unit test result:

  63275147
    ✓ should pass (2630ms)


  1 passing (3s)

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |   83.33 |      100 |      60 |   83.33 |                   
 a.js     |     100 |      100 |     100 |     100 |                   
 b.js     |     100 |      100 |     100 |     100 |                   
 c.js     |      50 |      100 |       0 |      50 | 3-8               
----------|---------|----------|---------|---------|-------------------

Collectives™ on Stack Overflow

How to mock nested dependencies in NodeJS

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related