CODEWITHSUNDEEP
javascriptjestjsjsdomrewire
Andreas Dolk
Andreas Dolk

Reputation: 114757

ReferenceError 'navigator is not defined' when using jest, jsdom and rewire

I'm stuck with a jest test setup. I want to test some client side code, an electron preload script, to be precise and want to use rewire to test methods that are not exported.

The script under test depends on a another script that accesses window.navigator. I can require the test script but it fails with a ReferenceError: navigator is not defined error on the first line in dom.js when I use rewire instead.

Here is a minimal setup that shows the error. I do not use a jest config as it defaults to the jsdom test enviroment.

dom.js

console.log('during rewire:', global.navigator)  // <-- prints undefined
console.log('The added property:', global.FOO)   // <-- prints undefined 

const userAgent = navigator.userAgent;           // <-- fails.

index.js

const myDom = require('./dom.js');

module.exports = {
  doSomething: () => {}
}

index.spec.js

const rewire = require('rewire');

describe('Basic test', () => {
  it('exports a function', () => {
    global.FOO = 'Bar'
    console.log('before rewire:', global.navigator)  // prints Navigator {}
    console.log('The added property:', global.FOO)   // prints Bar

    // const main = require('.')  // <-- works with require
    const main = rewire('.')      // <-- but fails with rewire
    expect(typeof main.doSomething).toBe('function');
  })
})

It looks as if rewire uses a different global, one that does not have the jsdom environment anymore (or not yet?) (like global.window.navigator or global.navigator).

Any help is highly appreciated, usually I find solutions for almost all problems on google but this time, I'm lost.

To reproduce, copy the three files to a folder, then do npm init, npm install jest rewire, npx jest.

Upvotes: 6

Views: 4532

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