Jest + process.env.NODE_ENV not testing properly

Question

I have a config file that changes a variable based on the process.env.NODE_ENV here is the function:

const { hostname } = window.location

let USE_DEV_TOOLS = false
if (
  hostname === 'qa.example.com' ||
  hostname === 'dev.example.com' ||
  NODE_ENV !== 'production'
) {
  USE_DEV_TOOLS = true
}

In my test I want to test that if NODE_ENV is production, USE_DEV_TOOLS returns false however, if I try to change the NODE_ENV it updates after getting the variable.

import config from 'consts/config'
describe('Environment variables', () => {
  const ORIGINAL_ENV = process.env
  beforeEach(() => {
    jest.resetModules()
    process.env = { ...ORIGINAL_ENV }
  })

  afterAll(() => {
    process.env = ORIGINAL_ENV
  })

  it('production does not use dev tools', () => {
    process.env = { NODE_ENV: 'production' }

    // console logs properly, but is changing after I get config
    console.log(process.env.NODE_ENV) 

    expect(config.USE_DEV_TOOLS).toBe(false)
  })
}) 

Answer 1

Use es6 import to import the module, the code in the module will be executed immediately, at this time process.env.NODE_ENV environment has not been modified.

So you should use require to require the module after modifying the process.env.NODE_ENV in the test case.

E.g.

config.js:

const { hostname } = window.location;

console.log('config loaded');

let USE_DEV_TOOLS = false;
if (hostname === 'qa.example.com' || hostname === 'dev.example.com' || process.env.NODE_ENV !== 'production') {
  USE_DEV_TOOLS = true;
}

export default { USE_DEV_TOOLS };

config.test.js:

describe('Environment variables', () => {
  const ORIGINAL_ENV = process.env;
  beforeEach(() => {
    jest.resetModules();
    process.env = { ...ORIGINAL_ENV };
  });

  afterAll(() => {
    process.env = ORIGINAL_ENV;
  });

  it('production does not use dev tools', () => {
    process.env = { NODE_ENV: 'production' };
    console.log(process.env.NODE_ENV);
    const config = require('./config').default;

    expect(config.USE_DEV_TOOLS).toBe(false);
  });
});

test result:

 PASS  examples/66555582/config.test.js
  Environment variables
    ✓ production does not use dev tools (10 ms)

  console.log
    production

      at Object.<anonymous> (examples/66555582/config.test.js:16:13)

  console.log
    config loaded

      at Object.<anonymous> (examples/66555582/config.js:3:9)

Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        1.392 s, estimated 4 s