add test case

Author: qchen-dev

__mocks__/fileMock.js

@@ -0,0 +1,2 @@
+// __mocks__/fileMock.js
+export default 'test-file-stub';

__mocks__/styleMock.js

@@ -0,0 +1,2 @@
+// __mocks__/styleMock.js
+export default {};

__tests__/App.spec.jsx

@@ -0,0 +1,16 @@
+import React from 'react';
+import { render, screen } from '@testing-library/react';
+import '@testing-library/jest-dom';
+import App from '../src/App';
+
+describe('App', () => {
+  it('renders the app heading and welcome message', () => {
+    render(<App />);
+
+    const heading = screen.getByRole('heading', { name: /docker \+ react/i });
+    const message = screen.getByText(/hello from docker react project/i);
+
+    expect(heading).toBeInTheDocument();
+    expect(message).toBeInTheDocument();
+  });
+});

babel.config.js

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+// babel.config.js
+export default {
+  presets: ['@babel/preset-env', '@babel/preset-react'],
+};

eslint.config.js

@@ -1,7 +1,7 @@
-import js from '@eslint/js'
-import globals from 'globals'
-import reactHooks from 'eslint-plugin-react-hooks'
-import reactRefresh from 'eslint-plugin-react-refresh'
+import js from '@eslint/js';
+import globals from 'globals';
+import reactHooks from 'eslint-plugin-react-hooks';
+import reactRefresh from 'eslint-plugin-react-refresh';
 
 export default [
   { ignores: ['dist'] },
@@ -30,4 +30,16 @@ export default [
       ],
     },
   },
-]
+  {
+    files: [
+      '**/*.test.{js,jsx}',
+      '**/*.spec.{js,jsx}',
+      '**/__tests__/**/*.{js,jsx}',
+    ],
+    languageOptions: {
+      globals: {
+        ...globals.jest,
+      },
+    },
+  },
+];

jest.config.js

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+// jest.config.js
+export default {
+  testEnvironment: 'jsdom',
+  transform: {
+    '^.+\\.[jt]sx?$': 'babel-jest',
+  },
+  moduleFileExtensions: ['js', 'jsx'],
+  // setupFilesAfterEnv: ['@testing-library/jest-dom'],
+  setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
+
+  moduleNameMapper: {
+    '\\.(css|less|scss|sass)$': '<rootDir>/__mocks__/styleMock.js',
+    '\\.(jpg|jpeg|png|gif|svg)$': '<rootDir>/__mocks__/fileMock.js',
+  },
+};

jest.setup.js

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+import '@testing-library/jest-dom';