首先，您可能不需要对此进行测试，但您绝对可以。
如果你真的想这么做，你需要重新构造你的代码，这样就有一个函数要测试：

// Import dependencies
import React from 'react';
import { render } from 'react-dom';
import { browserHistory } from 'react-router';
import { syncHistoryWithStore } from 'react-router-redux';
import configureStore from './store/configureStore';
import Root from './containers/Root';

export const app = () => {
   const store = configureStore({});
   const history = syncHistoryWithStore(browserHistory, store);

   render(
     <Root store={store} history={history} />,
     document.getElementById('react')
   );
};

然后，您可以使用react testing库之类的工具来确保将Root组件挂载到正确的元素中：

import { render, screen } from '@testing-library/react';
import { app } from './app';

test('app should render the Root component into the expected element', () => {
   // render the document with the element we plan on using for our react app
   render(<div id="react" />);

   // invoke the function that will render our component into that element
   app();

   // assert that the component exists in the document
   // you can mock `Root` to be some element you expect to see in the test
   // for the sake of this example, since I know nothing about `Root`
   // let's assume it has some identifying text
   expect(screen.getByText('rooty tooty toot toot')).toBeInTheDocument(); 
});

这样我们就可以在入口点用文本显示所做的工作，但现在它是一个需要调用的函数！要使应用正常工作，入口点需要导入app函数并调用它：

import { app } from './app';

app();