jest testEnvironment jsdom window is not defined

TL;DR

Since Jest 28 the default test environment is node, not jsdom, so window does not exist unless you opt in. Install jest-environment-jsdom and set testEnvironment: 'jsdom' in the Jest config. That one change fixes every window is not defined failure at once.

Error

ReferenceError: window is not defined
  at Object.[anonymous] (src/components/Button.test.js:3:1)

Steps

1. Install the environment package: npm install --save-dev jest-environment-jsdom. Expected: it appears in devDependencies.
2. Set testEnvironment: 'jsdom' in jest.config.js (or under the jest key in package.json). Expected: the config loads with no "test environment not found" error.
3. Re-run the suite. Expected: window, document, and other DOM APIs resolve in tests.

When to use

• window is not defined (or document is not defined) after upgrading to Jest 28+.
• A fresh Jest install where component tests touch the DOM.
• You relied on the old default and never set testEnvironment explicitly.

When not to use

• The error comes from a bundler or a real browser runtime, not Jest.
• Fine-tuning jsdom behavior (url, pretendToBeVisual) once the environment loads.
• You are on Jest 27 or earlier (jsdom was the default there).

Tool compatibility

• Jest 28, 29, and 30 with a matching jest-environment-jsdom major version.
• Jest 27 and earlier need no change (jsdom was the default).

Variant phrasings

jest window is not defined after upgrading to jest 28

The upgrade changed the default environment; this is the fix.

ReferenceError document is not defined jest

Same cause and same fix; document comes from the same jsdom environment.

Why it happens

Jest 27 and earlier defaulted to jsdom. Jest 28 flipped the default to node for speed and split jsdom into a separate package you must install. Tests written against the old default break with window is not defined until you opt back in.

Edge cases

• Some tests need node (API tests): set the environment per file with a docblock pragma instead of globally.
• Still fails after the fix: you may have two Jest versions installed; check which config the runner actually loads.
• The jest-environment-jsdom major version must match your Jest major version.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_W5wHBlHeVOziP8l4Y-dsQw