readded essential files

package.json

@@ -10,11 +10,13 @@
   },
   "scripts": {
     "start": "react-scripts start",
-    "build": "react-scripts build"
+    "build": "react-scripts build",
+    "test": "react-scripts test"
   },
   "eslintConfig": {
     "extends": [
-      "react-app"
+      "react-app",
+      "react-app/jest"
     ]
   },
   "browserslist": {

src/App.test.js

@@ -0,0 +1,8 @@
+import { render, screen } from '@testing-library/react';
+import App from './App';
+
+test('renders learn react link', () => {
+  render(<App />);
+  const linkElement = screen.getByText(/learn react/i);
+  expect(linkElement).toBeInTheDocument();
+});