import {create, act} from 'react-test-renderer';import App from './app.js'; // The component being tested// render the componentlet root; act(() => {
  root = create(<App value={1}/>)});// make assertions on root expect(root.toJSON()).toMatchSnapshot();// update with some different propsact(() => {
  root.update(<App value={2}/>);})// make assertions on root expect(root.toJSON()).toMatchSnapshot();