App2.test.js

App.test.js

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

test('changes application state', () => { 
  render(<App />); 
  const buttonElement = screen.getByRole('button'); 
  expect(buttonElement).toBeInTheDocument(); 
  expect(screen.queryByText('Click the button')).toBeInTheDocument();  
  expect(screen.queryByText('Pressed!')).toBeNull(); 
  fireEvent.click(buttonElement); 
  expect(screen.queryByText('Click the button')).toBeNull();  
  expect(screen.queryByText('Pressed!')).toBeInTheDocument(); 
});