jest.config.js

@@ -0,0 +1,14 @@
+export default {
+  preset: 'ts-jest/presets/default-esm',
+  testEnvironment: 'jsdom',
+  extensionsToTreatAsEsm: ['.ts', '.tsx'],
+  setupFilesAfterEnv: ['<rootDir>/test/setupTests.ts'],
+  moduleNameMapper: {
+    '^@/(.*)$': '<rootDir>/src/$1',
+    '\\.(css|scss|sass)$': 'identity-obj-proxy'
+  },
+  testMatch: ['<rootDir>/test/*.test.(ts|tsx)'],
+  transform: {
+    '^.+\\.(ts|tsx)$': ['ts-jest', { useESM: true, tsconfig: 'tsconfig.jest.json' }]
+  }
+};

package.json

@@ -16,6 +16,10 @@
   },
   "devDependencies": {
     "@eslint/js": "^9.36.0",
+    "@testing-library/jest-dom": "^6.9.1",
+    "@testing-library/react": "^16.3.0",
+    "@testing-library/user-event": "^14.6.1",
+    "@types/jest": "^30.0.0",
     "@types/react": "^19.1.13",
     "@types/react-dom": "^19.1.9",
     "@vitejs/plugin-react": "^5.0.3",
@@ -23,6 +27,10 @@
     "eslint-plugin-react-hooks": "^5.2.0",
     "eslint-plugin-react-refresh": "^0.4.20",
     "globals": "^16.4.0",
+    "identity-obj-proxy": "^3.0.0",
+    "jest": "^30.2.0",
+    "jest-environment-jsdom": "^30.2.0",
+    "ts-jest": "^29.4.5",
     "typescript": "~5.8.3",
     "typescript-eslint": "^8.44.0",
     "vite": "^7.1.7"

test/components.test.tsx

@@ -0,0 +1,12 @@
+import userEvent from '@testing-library/user-event';
+import { render, screen} from '@testing-library/react';
+import Counter from '../src/components/components';
+
+describe('Counter component', () => {
+  test('increments count', async () => {
+    render(<Counter />);
+    const button = screen.getByRole('button', { name: /count is 0/i });
+    await userEvent.click(button);
+    expect(screen.getByText(/count is 1/i)).toBeInTheDocument();
+  });
+});

test/setupTests.ts

@@ -0,0 +1,2 @@
+// Adds jest-dom matchers for React testing library
+import '@testing-library/jest-dom';

tsconfig.app.json

@@ -24,5 +24,5 @@
     "noFallthroughCasesInSwitch": true,
     "noUncheckedSideEffectImports": true
   },
-  "include": ["src"]
+  "include": ["src","test"]
 }

tsconfig.jest.json

@@ -0,0 +1,12 @@
+{
+  "extends": "./tsconfig.app.json",
+  "compilerOptions": {
+    "verbatimModuleSyntax": false,
+    "jsx": "react-jsx",
+    "module": "ESNext",
+    "target": "ES2022",
+    "allowJs": true,
+    "esModuleInterop": true
+  },
+  "include": ["test"]
+}