App.js

import React, {Component} from 'react';
import './App.css';
import TestComponent from "./TestComponent";

class App extends Component {
    read = 'hi from app';

    render() {
    return (
      <div className="App">
        <TestComponent hello={this.read}/>
      </div>
    );
  }
}

export default App;

TestComponent.js

import React from 'react';

class TestComponent extends React.Component {
    render() {
        return (
        <div>

     {/*       //    Unresolved variable hello
            //Inspection info: Checks JavaScript referenced variables and fields to be valid ones.
           // The validation works in JavaScript, html or jsp files*/}
            {this.props.hello}
            </div>
        )
    }
}

export default TestComponent;