export variable from class React

You could make test a static property on the App class, then just reference it from the App class since that is exported.

class Test extends React.Component {
  static test = true;
}

console.info(Test.test);

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>

import Test from 'test';
console.info(Test.test);

Assuming your intention with test is to define something like a "project constant" (which is what I gather, from your use of the const keyword), then you could simply declare test outside of the App class, and then export it from the module in the same way you are exporting the class:

/*
Export test variable
*/
export const test = true;

/*
Export your App class
*/
export class App extends Component {
    static propTypes = {
        //somecode
    };

    constructor(...args: any): void {
        super(...args);
    }

    render() {
        /*
        Access test variable in "global scope" inside render method
        */
        console.log(`test is: ${ test }`);

        // console.log('app render start');
        // const test = true;
        return (
        //somecode
        );
    }

    componentDidMount() {
        //somecode
    }


    componentDidUpdate(prevProps): void {
        //somecode
    }
}

And then, from another module in your project you could access test like so:

import { App, test, } from 'path/to/App';

console.log(`test is: ${ test }`);