Reactjs: document is not defined

Ensure you add this code documentation block at the top of the your test file

/**
 * @jest-environment jsdom
 */

if you're rendering this server side, there will be no "document" object. try wrapping it in the following:

if (typeof window !== 'undefined') {
    React.render(<MainWrapper />, document.getElementById("root"));
}

this will check to see if a window object is present - meaning its in the browser - which also means that the document object is present

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to keep this answer valid

Newer versions of React have been split into multiple packages, you will need to import from react-dom now:

import ReactDOM from 'react-dom';

if (typeof window !== 'undefined') {
    ReactDOM.render(<MainWrapper />, document.getElementById("root"));
}