Warning: An update to App inside a test was not wrapped in act(...).

When testing, code that causes React state updates should be wrapped into act(...):

act(() => {
  /* fire events that update state */
});
/* assert on the output */

This ensures that you're testing the behavior the user would see in the browser. Learn more at https://fb.me/react-wrap-tests-with-act
    in App (at App.spec.js:52)

console.error node_modules/react-dom/cjs/react-dom.development.js:88
Warning: An update to App inside a test was not wrapped in act(...).

When testing, code that causes React state updates should be wrapped into act(...):

act(() => {
  /* fire events that update state */
});
/* assert on the output */

This ensures that you're testing the behavior the user would see in the browser. Learn more at https://fb.me/react-wrap-tests-with-act
    in App (created by WrapperComponent)
    in WrapperComponent

I have a simple component that has ref attribute
In the useLayoutEffect I am calculating isShown value to show or hide <div id="isShown">XYZ</div> element based on divRef.current.offsetWidth.
here is my code example

import React, { useRef, useLayoutEffect, useState } from 'react';

export default function MyComponent() {
const [isShown, setIsShown] = useState(false);
const divRef = useRef(null);

useLayoutEffect(() => {
if (divRef.current) {
setIsShown(divRef.current.offsetWidth > 0)
}
}, [divRef])

return (
<div id="myDiv" ref={divRef}>
{isShown && <div id="isShown">XYZ</div>}
</div>
);
}

And I want to write some unit tests for it. So I am trying to mock useRef current.offsetWidth to set it to 123 (as example) - but it is always equal to 0.
Any suggestions on what could be wrong here?
the is an example

import React from 'react';
import { configure, mount } from 'enzyme';
import MyComponent from './Comp';
import Adapter from "enzyme-adapter-react-16";

configure({ adapter: new Adapter() })

describe('MyComponent', () => {

it('should pass', () => {
jest.spyOn(React, "useRef").mockReturnValue({
current: {
offsetWidth: 123
}
});
const wrapper = mount(<MyComponent></MyComponent>);
expect(wrapper.find('#isShown')).toHaveLength(1);
});
});

The devDependency webpack was updated from 4.37.0 to 4.38.0.

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The devDependency start-server-and-test was updated from 1.10.2 to 1.10.3.

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start-server-and-test is a devDependency of this project. It might not break your production code or affect downstream projects, but probably breaks your build or test tools, which may prevent deploying or publishing.

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The devDependency react-hot-loader was updated from 4.12.9 to 4.12.10.

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react-hot-loader is a devDependency of this project. It might not break your production code or affect downstream projects, but probably breaks your build or test tools, which may prevent deploying or publishing.

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☝️ Important announcement: Greenkeeper will be saying goodbye 👋 and passing the torch to Snyk on June 3rd, 2020! Find out how to migrate to Snyk and more at greenkeeper.io

There have been updates to the babel7 monorepo:

• • The devDependency @babel/core was updated from 7.8.7 to 7.9.0.

• The devDependency @babel/node was updated from 7.8.4 to 7.8.7.
• The devDependency @babel/preset-env was updated from 7.8.7 to 7.9.0.
• The devDependency @babel/preset-react was updated from 7.8.3 to 7.9.0.

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This version is covered by your current version range and after updating it in your project the build failed.

This monorepo update includes releases of one or more dependencies which all belong to the babel7 group definition.

babel7 is a devDependency of this project. It might not break your production code or affect downstream projects, but probably breaks your build or test tools, which may prevent deploying or publishing.

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