Jest Installation Guide

Installation for TypeScript

1) Install Jest and TypeScript Dependencies

Run the following command:

npm i -D jest typescript ts-jest @types/jest

2) Configure jest.config.ts Manually

import type { Config } from '@jest/types';

const config: Config.InitialOptions = {
  preset: 'ts-jest',
  testEnvironment: 'jsdom',  // Use 'jsdom' for React, 'node' for backend
  verbose: true,
  transform: {
    '^.+\\.tsx?$': ['ts-jest', { tsconfig: 'tsconfig.json' }],
  },
  moduleNameMapper: {
    '^@/(.*)$': '<rootDir>/src/$1', // Ensure alias resolution
  }
};

export default config;

3) Install ts-node dependency

ts-node is a TypeScript execution environment for Node.js. It allows you to run TypeScript files directly without needing to compile them into JavaScript first. Run the following command:

npm i -D ts-node

4) Update Ts-config

Ensure your tsconfig.json file contains the following options:

{
  "compilerOptions": {
    "jsx": "react-jsx", // Enables JSX support
    "esModuleInterop": true, // Fix import issues
    "moduleResolution": "node",
    "baseUrl": "./",
    "paths": {
      "@/*": ["src/*"] // Ensure alias resolution
    }
  }
}

Installation for JavaScript

1) Install Jest

Run the following command:

npm i --save-dev jest

2) Update package.json

Modify the scripts section in package.json to include Jest:

"scripts": {
  "test": "jest"
}

---

After writing the test, run the following command in your command line to execute the tests:

npm test

Note:
After running npm test, Jest will detect files with extensions like .spec or .test. For example, your-file-name.spec.tsx or your-file-name.test.tsx. Make sure you have written all the test cases in these files.