Jest test fails with window is not defined

I had the same issue and I do not believe modifying globals is the way to do it. The issue was because in my jest config I had testEnvironment set to node when it should've been jsdom. For me this setting was located in package.json as defined by the react starter app.

In your package.json add window like global something like this

"jest": {
  "verbose": true,
  "preset": "react-native",
  "setupFiles": ["./jest/setup.js"],
  "testRegex": "(/tests/.*|\\.(test|spec))\\.(ts|tsx|js)$",
  "transformIgnorePatterns": [
    "node_modules/(?!(jest-)?react-native|lottie-react-native)"
  ],
  "globals": {
    "window": {}
  }
}

2021 (Jest 27)

Jest's testEnvironment default used to be jsdom. It was changed to node recently starting with version 27.

You can set testEnvironment: 'jsdom' in your config file to keep using JSDOM.

However 'node' seems to be a lot faster, so you should be mocking browser APIs where possible.

https://jestjs.io/blog/2021/05/25/jest-27

npm i jest-environment-jsdom

index.test.tsx

/**
 * @jest-environment jsdom
 */