🚀 Elevate Code Quality in 6 Steps: Setting Up Unit Testing with Jest and TypeScript

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Unit testing is the backbone of ensuring software quality, and when combined with TypeScript, it becomes a potent tool for crafting reliable and maintainable code. In this comprehensive guide, we'll walk you through the process of setting up unit testing using the popular testing framework, Jest, in a TypeScript project.

Prerequisites

Before we begin, make sure you have Node.js and npm (Node Package Manager) installed on your system. You can download them from the official Node.js website.

Step 1: Initialize Your Project

Start by creating a new directory for your project and navigate into it using the terminal.

mkdir my-typescript-project
cd my-typescript-project

Initialize your project by running:

npm init -y

This command will create a package.json file with default settings.

Step 2: Install Dependencies

Next, we need to install the necessary dependencies: Jest and ts-jest. Jest is the testing framework, and ts-jest enables Jest to work seamlessly with TypeScript.

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

Step 3: Configure TypeScript

Create a tsconfig.json file in the root of your project. You can initialize it by running:

npx tsc --init

Open the tsconfig.json file and make sure the following options are set:

{
  "compilerOptions": {
    "target": "ES6",
    "module": "CommonJS",
    "strict": true,
    "esModuleInterop": true
  }
}

Step 4: Configure Jest

Create a jest.config.js file in the project root and add the following configuration:

module.exports = {
  preset: 'ts-jest',
  testEnvironment: 'node',
};

Step 5: Write Your First Test

Create a directory named src in your project folder. Inside the src directory, create a file named example.ts with a simple function:

// src/example.ts

export function add(a: number, b: number): number {
  return a + b;
}

Now, let's write a test for this function. Create a directory named __tests__ in the root of your project, and inside it, create a file named example.test.ts:

// __tests__/example.test.ts

import { add } from '../src/example';

test('add function adds two numbers correctly', () => {
  expect(add(2, 3)).toBe(5);
});

Step 6: Run Your Tests

Add a test script to your package.json:

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

Now, you can run your tests using:

npm test

Congratulations! You've successfully set up unit testing with Jest in a TypeScript project. This foundation will enable you to write tests that catch bugs early and ensure the reliability of your codebase. As your project grows, you can explore more advanced testing techniques and strategies to create even more robust software.

Remember, unit testing is not just about catching bugs – it's also about building confidence in your code. Happy testing!

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💡 Trivia Corner

Namespaces were formerly known as "Internal Modules" in earlier versions of TypeScript.

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