Tillitsdone
down Scroll to discover

Mastering Jest Hooks: Before and After Guide

Learn how to effectively use Jest's Before and After hooks to write cleaner, more maintainable tests.

Discover best practices, common patterns, and avoid pitfalls in test setup and teardown.
thumbnail

Close-up macro shot of a pristine clear crystal structure with emerald green color gradients showcasing intricate geometric patterns captured with a tilt-shift lens high-quality ultra-realistic cinematic 8K UHD high resolution sharp and detail

Effective Use of Before/After Hooks in Jest

Testing is an art, and like any masterpiece, it requires the right tools and techniques. One of the most powerful features in Jest is its suite of hooks - beforeAll, beforeEach, afterAll, and afterEach. Let’s dive into how we can leverage these hooks effectively to write cleaner, more maintainable tests.

Understanding the Basics

Before and After hooks in Jest are like the stagehands of a theater production - they set up and clean up behind the scenes, ensuring everything runs smoothly. These hooks help us maintain a clean testing environment and reduce code duplication.

Abstract architectural interior with soft dusty blue light streaming through geometric windows captured from a low angle perspective creating dramatic shadows and highlights high-quality ultra-realistic cinematic 8K UHD high resolution sharp and detail

Common Use Cases

Database Connections

One of the most common use cases for hooks is managing database connections. Here’s how you might structure your tests:

let db;
beforeAll(async () => {
db = await connect();
});
afterAll(async () => {
await db.close();
});
test('should save user to database', async () => {
// Your test here
});

State Reset

For tests that modify shared state, beforeEach and afterEach are your best friends:

let user;
beforeEach(() => {
user = {
name: 'John Doe',
email: 'john@example.com'
};
});
test('should update user name', () => {
user.name = 'Jane Doe';
expect(user.name).toBe('Jane Doe');
});
test('should have original name', () => {
expect(user.name).toBe('John Doe');
});

Abstract minimalist composition of concrete textures and stark white geometric shapes against a black background shot from a bird's eye view perspective high-quality ultra-realistic cinematic 8K UHD high resolution sharp and detail

Best Practices

  1. Keep Hooks Simple Your hooks should be focused and straightforward. If you find yourself writing complex logic in hooks, consider moving that logic into helper functions.

  2. Scope Your Hooks Appropriately Use describe blocks to scope your hooks. This helps maintain clarity about which setup and teardown code applies to which tests.

  3. Clean Up After Yourself Always clean up any resources you’ve created. This includes closing database connections, clearing mocks, and resetting any modified global state.

  4. Use Mock Restoration When working with mocks, take advantage of Jest’s automatic mock restoration in combination with hooks:

const mock = jest.fn();
beforeEach(() => {
mock.mockClear();
});
test('should call mock once', () => {
mock();
expect(mock).toHaveBeenCalledTimes(1);
});

Advanced Patterns

Sometimes you need more complex setup and teardown logic. Here’s a pattern for handling nested hooks:

describe('User API', () => {
beforeAll(() => {
// Setup for all user tests
});
describe('authentication', () => {
beforeEach(() => {
// Setup specifically for auth tests
});
test('should authenticate valid user', () => {
// Test code
});
});
});

Common Pitfalls to Avoid

  1. Don’t make hooks dependent on test execution order
  2. Avoid sharing state between tests unless absolutely necessary
  3. Keep async operations properly handled with async/await
  4. Don’t skip cleanup in afterEach/afterAll hooks

Remember, the goal of hooks is to make your tests more maintainable and reliable. Use them wisely, and they’ll serve as powerful allies in your testing arsenal.

Dramatic close-up of a metallic navy blue surface with reflective properties creating abstract patterns captured from a diagonal angle with shallow depth of field high-quality ultra-realistic cinematic 8K UHD high resolution sharp and detail

icons/logo-tid.svg Latest Blogs
Discover our top articles, selected to support the growth of your business.
https://imgproxy-landing-page.tillitsdone.com/sig/rs:fit:1200:630/plain/https%3A%2F%2Fcms-r2.tillitsdone.com%2Fwp-content-prod%2Fuploads%2F2025%2F10%2FTill-its-done_SEO_R43_Sep_1440x697.jpg@webp สร้างเว็บไซต์ 1 เว็บ ต้องใช้งบเท่าไหร่? เจาะลึกทุกองค์ประกอบ website development cost อยากสร้างเว็บไซต์แต่ไม่มั่นใจในเรื่องของงบประมาณ อ่านสรุปเจาะลึกตั้งแต่ดีไซน์, ฟังก์ชัน และการดูแล พร้อมตัวอย่างงบจริงจาก Till it’s done ที่แผนชัด งบไม่บานปลายแน่นอน https://imgproxy-landing-page.tillitsdone.com/sig/rs:fit:1200:630/plain/https%3A%2F%2Fcms-r2.tillitsdone.com%2Fwp-content-prod%2Fuploads%2F2025%2F10%2FTill-its-done_SEO_R42_Sep_1440x697.jpg@webp Next.js สอน 14 ขั้นตอนเบื้องต้น: สร้างโปรเจกต์แรกใน 30 นาที เริ่มต้นกับ Next.js ใน 14 ขั้นตอนเพียงแค่ 30 นาที พร้อม SSR/SSG และ API Routes ด้วยตัวอย่างโค้ดง่าย ๆ อ่านต่อเพื่อสร้างโปรเจ็กต์แรกได้ทันทีที่นี่ https://imgproxy-landing-page.tillitsdone.com/sig/rs:fit:1200:630/plain/https%3A%2F%2Fcms-r2.tillitsdone.com%2Fwp-content-prod%2Fuploads%2F2025%2F10%2FTill-its-done_SEO_R41_Sep_1440x697.jpg@webp วิธีสมัคร Apple Developer Account เพื่อนำแอปขึ้น App Store ทีละขั้นตอน อยากปล่อยแอปบน App Store ระดับโลก มาอ่านคู่มือสมัคร Apple Developer Account พร้อมเคล็ดลับ TestFlight และวิธีอัปโหลดที่ง่ายในบทความเดียวนี้ได้เลย https://imgproxy-landing-page.tillitsdone.com/sig/rs:fit:1200:630/plain/https%3A%2F%2Fcms-r2.tillitsdone.com%2Fwp-content-prod%2Fuploads%2F2025%2F10%2FTill-its-done_SEO_R38_Sep_1440x697.jpg@webp TypeScript Interface คืออะไร? อธิบายพร้อมวิธีใช้และข้อแตกต่างจาก Type เรียนรู้วิธีใช้ TypeScript Interface เพื่อสร้างโครงสร้างข้อมูลที่ปลอดภัยและเข้าใจง่าย พร้อมเปรียบเทียบข้อดีข้อแตกต่างกับ Type ที่คุณต้องรู้ ถูกรวมเอาไว้ในบทความนี้แล้ว https://imgproxy-landing-page.tillitsdone.com/sig/rs:fit:1200:630/plain/https%3A%2F%2Fcms-r2.tillitsdone.com%2Fwp-content-prod%2Fuploads%2F2025%2F09%2FTill-its-done_SEO_R36_Sep_1440x697.jpg@webp Material-UI (MUI) คืออะไร อยากสร้าง UI สวยงามและเป็นมืออาชีพในเวลาอันรวดเร็วใช่ไหม มาทำความรู้จักกับ Material-UI (MUI) ที่ช่วยให้คุณพัฒนาแอปพลิเคชันบน React ได้ง่ายและดูดีในทุกอุปกรณ์ https://imgproxy-landing-page.tillitsdone.com/sig/rs:fit:1200:630/plain/https%3A%2F%2Fcms-r2.tillitsdone.com%2Fwp-content-prod%2Fuploads%2F2025%2F09%2FTill-its-done_SEO_R27_Sep_1440x697.jpg@webp เปรียบเทียบ 3 วิธีติดตั้ง install node js บน Ubuntu: NVM vs NodeSource vs Official Repo แบบไหนดีที่สุด? เรียนรู้วิธีติดตั้ง Node.js บน Ubuntu ด้วย NVM, NodeSource หรือ Official Repo เลือกวิธีที่เหมาะกับความต้องการของคุณ พร้อมเปรียบเทียบ เพื่อการพัฒนาที่มีประสิทธิภาพ!
icons/logo-tid.svg

Talk with CEO

Ready to bring your web/app to life or boost your team with expert Thai developers?
Contact us today to discuss your needs, and let’s create tailored solutions to achieve your goals. We’re here to help at every step!
🖐️ Contact us
down Explore our best articles, cover a wide variety of technologies
Our knowledge base
196 Articles
Explore right
icons/logo-react.svg ReactJs
Popular JavaScript library for building user interfaces with a component-based architecture.
160 Articles
Explore right
icons/flutter.svg Flutter
UI toolkit for building natively compiled applications for mobile, web, and desktop from a single codebase.
144 Articles
Explore right
icons/logo-nodejs.svg Nodejs
JavaScript runtime for building scalable, high-performance server-side applications.
58 Articles
Explore right
icons/next-js.svg Nextjs
React framework enabling server-side rendering and static site generation for optimized performance.
38 Articles
Explore right
icons/tailwind.svg TailwindCSS
Utility-first CSS framework for rapid UI development.
36 Articles
Explore right
icons/code-outline.svg Typescript
Superset of JavaScript adding static types for improved code quality and maintainability.
126 Articles
Explore right
icons/code-outline.svg Golang
Programming language known for its simplicity, concurrency model, and performance.
67 Articles
Explore right
icons/code-outline.svg AstroJs
Astro is an all-in-one web framework. It includes everything you need to create a website, built-in.
38 Articles
Explore right
icons/code-outline.svg Jest
Versatile testing framework for JavaScript applications supporting various test types.
16 Articles
Explore right
icons/code-outline.svg Website development th
11 Articles
Explore right
icons/code-outline.svg Mobile application th
5 Articles
Explore right
icons/code-outline.svg Reactjs th
4 Articles
Explore right
icons/code-outline.svg Nextjs th
3 Articles
Explore right
icons/code-outline.svg Flutter th
1 Articles
Explore right
icons/code-outline.svg Software house th
1 Articles
Explore right
icons/code-outline.svg Nodejs th
1 Articles
Explore right
icons/code-outline.svg Typescript th
337 Articles
Explore right
icons/css-4.svg CSS
CSS3 is the latest version of Cascading Style Sheets, offering advanced styling features like animations, transitions, shadows, gradients, and responsive design.
Let's keep in Touch
Thank you for your interest in Tillitsdone! Whether you have a question about our services, want to discuss a potential project, or simply want to say hello, we're here and ready to assist you.
We'll be right here with you every step of the way.
Contact Information
rick@tillitsdone.com+66824564755
Find All the Ways to Get in Touch with Tillitsdone - We're Just a Click, Call, or Message Away. We'll Be Right Here, Ready to Respond and Start a Conversation About Your Needs.
Address
9 Phahonyothin Rd, Khlong Nueng, Khlong Luang District, Pathum Thani, Bangkok Thailand
Visit Tillitsdone at Our Physical Location - We'd Love to Welcome You to Our Creative Space. We'll Be Right Here, Ready to Show You Around and Discuss Your Ideas in Person.
Social media
FacebookInstagramLinkedIn
Connect with Tillitsdone on Various Social Platforms - Stay Updated and Engage with Our Latest Projects and Insights. We'll Be Right Here, Sharing Our Journey and Ready to Interact with You.
We anticipate your communication and look forward to discussing how we can contribute to your business's success.
We'll be here, prepared to commence this promising collaboration.
Frequently Asked Questions
Explore frequently asked questions about our products and services.
Whether you're curious about features, warranties, or shopping policies, we provide comprehensive answers to assist you.