import React, { Component } from 'react';

class App extends Component {
  render() {
    return (
        <div>Teste</div>
    );
  }
}

export default App;

import React, { Component } from 'react';

class App extends Component {
  render() {
    return (
        <div>React Bootstrap is working!</div>
    );
  }
}

export default App;

Change success phrase in App.js