[node][mocha]Global variables not accessible when testing with mocha

问题

I'm trying to create a unit test for express node application. I want the configuration used for the test to be different than the one used in production, so I implemented the following.

In my index.js, I load the configuration into the global variable like this:

global.env = {};
global.env.config = require('./config/config');
// Create the server ...
server.listen(3000);

module.exports = server;

In some other controller myController.js, I access the global variable like this

var Config = global.env.config

When I launch this using node index.js it works just fine.

But when I use mocha with proxyquire to override the config:

describe('myController', function () {
    describe("#myMethod", () => {

        it("must work", (done) => {
             const config = {
                INPUT_FILE_DIR: path.resolve('../ressources/input/')
             }

             const server = proxyquire('../index.js', { './config/config': config })// error in this line
        })
    })
})

I have an error telling that myController can't read the property config

Cannot read property 'config' of undefined

Thanks for your help

回答1:

This is how I would have approached it. Firstly, i would export config as a function instead of an object.

The reason is the code will have a better structure and easy to maintain. Also there's no need to expose the config globally, as that could pose some security risk.

export const getConfig = () => {
  if(process.env.NODE_ENV==="production"){
    return require('./production.config');
  }
  return require('./default.config');
};

In my test file, I would mock the function call using sinonjs like below.

const configModule = require("./config");
sinon.stub(configModule, "getConfig").returns(require('./e2e.config'));

This is not a tested code, but I a bit certain that this pattern of thought should work.

回答2:

Why not just overwrite it with the new config in your test case.

E.g.

index.js:

const express = require('express');
const server = express();
const userController = require('./userController');

global.env = {};
global.env.config = require('./config');

server.get('/api/user', userController.getUser);

if (require.main === module) {
  const port = 3000;
  server.listen(port, () => {
    console.log(`HTTP server is listening on http://localhost:${port}`);
  });
}

module.exports = server;

userController.js:

const Config = global.env.config;

const userController = {
  getUser(req, res) {
    res.json(Config.user);
  },
};

module.exports = userController;

config.js:

module.exports = {
  user: { name: 'james' },
};

userController.test.js:

const sinon = require('sinon');

describe('userController', () => {
  describe('#getUser', () => {
    it('should pass', () => {
      global.env = {};
      global.env.config = { user: { name: 'jane' } };
      const userController = require('./userController');
      const mReq = {};
      const mRes = { json: sinon.stub() };
      userController.getUser(mReq, mRes);
      sinon.assert.calledWithExactly(mRes.json, { name: 'jane' });
    });
  });
});

unit test results with coverage report:

  userController
    #getUser
      ✓ should pass (880ms)


  1 passing (893ms)

-------------------|---------|----------|---------|---------|-------------------
File               | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
-------------------|---------|----------|---------|---------|-------------------
All files          |     100 |      100 |     100 |     100 |                   
 userController.js |     100 |      100 |     100 |     100 |                   
-------------------|---------|----------|---------|---------|-------------------

UPDATE

index.js:

// Order is matter, assign config to global firstly, then the controllers can access it.
global.env = {};
global.env.config = require('./config');

const express = require('express');
const server = express();
const userController = require('./userController');

server.get('/api/user', userController.getUser);

if (require.main === module) {
  const port = 3000;
  server.listen(port, () => {
    console.log(`HTTP server is listening on http://localhost:${port}`);
  });
}

module.exports = server;

userController.js and config.js are same as above.

index.test.js:

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

describe('60990025', () => {
  it('should get user', (done) => {
    const config = { user: { name: 'jane' } };
    const server = proxyquire('./', {
      './config': config,
    });
    request(server)
      .get('/api/user')
      .expect(200)
      .end((err, res) => {
        if (err) return done(err);
        expect(res.body).to.be.eql({ name: 'jane' });
        done();
      });
  });
});

API test results with coverage report:

  60990025
    ✓ should get user (2946ms)


  1 passing (3s)

-------------------|---------|----------|---------|---------|-------------------
File               | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
-------------------|---------|----------|---------|---------|-------------------
All files          |   81.25 |       50 |      50 |   81.25 |                   
 config.js         |     100 |      100 |     100 |     100 |                   
 index.js          |   72.73 |       50 |       0 |   72.73 | 12-14             
 userController.js |     100 |      100 |     100 |     100 |                   
-------------------|---------|----------|---------|---------|-------------------

source code: https://github.com/mrdulin/expressjs-research/tree/master/src/stackoverflow/60990025

来源：https://stackoverflow.com/questions/60990025/nodemochaglobal-variables-not-accessible-when-testing-with-mocha