Jest is a comprehensive JavaScript testing framework developed by Facebook. Its robust features and ease of use have made it a popular choice among developers for automating unit, integration, and snapshot testing in JavaScript applications.
What Makes Jest Stand Out?
Jest comes embedded with multiple features, taking away the inconvenience of using different packages for a complete automation tool. Its off-the-shelf features include built-in mocking, snapshot testing, and code coverage measurement. Additionally, it is useful in ensuring better code coverage in unit tests and providing substantial end-to-end coverage for APIs and Node.JS-based frontends.
Since Jest shares many core principles with Mocha, teams using frameworks such as mocha, chai, and axios can transition to Jest with minimal alterations to their scripts. This allows them to benefit from Jest’s additional tools.
Key Jest Features
Jest offers a host of features and concepts to enhance the testing process:
- Automated Testing
- Built-in Assertions
- Mocking
- Snapshot Testing
- Test Runners
- Test Suites and Test Cases
- Asynchronous Testing
- Code Coverage
- Configuration
- Extensibility
However, there may be downsides to using Jest over other JS-based approaches, notably a lack of modularity and customization. Jest enforces the use of its in-built libraries and features which, despite being streamlined, may limit teams with a strong preference for other node packages.
Getting Started with Jest
To begin using Jest, install it as a project dependency via a package manager such as npm or yarn. Define your test suites, test cases, and assertions using the describe, it, and expect syntax in your test files.
Check out this simple Jest test:
## Running your tests is typically as simple as executing the command `npm test` or `yarn test`, based on your project setup.
## Jest's Versatility
Jest is adaptable and can be utilized in assortment of JavaScript projects. Its simplicity, built-in features, and strong community support contribute to its widespread adoption for testing JavaScript applications.
The image above shows the exponential growth of Jest from 2016 to 2019.
## A Brief History of Jest
- 2013: Jest is launched.
- 2014: Jest gains support.
- 2015: Jest rises in popularity.
- 2016: Jest's growth accelerates.
- 2017: Jest's features expand.
- 2018: Jest matures with more features and use cases.
- 2019: Continued strong support from Facebook and a dedicated user base result in Jest's rapid development.
- 2020: Jest further improves, pleasing developers with its innovation.
- 2021: Despite possible tech debt, Jest stands strong, thanks to regular maintenance.
## Pros and Cons of Using Jest
### Pros:
- Easy setup and configuration
- Built-in Mocking
- Snapshot Testing
- Fast test Execution
- Comprehensive assertion library
- Automatic test watching
- Code coverage reporting
- Strong community support and active development
- Support for asynchronous testing
### Cons:
- Large bundle size
- Learning curve for advanced features
- Snapshot maintenance
- Opinionated configuration
- Global scope
- Complexity for smaller projects
- Performance impact
## When to Choose Jest for Testing
Consider using Jest in these scenarios:
- When you require a Node.JS tool for your CI/CD pipelines, but desire ease of maintenance.
- When you want a single tool for unit tests, integration tests, and end-to-end tests for web-based applications.
- If your testing team is developer-centric and comfortable working with open-source technologies.
Jest enjoys widespread usage and respect in the JavaScript community, and its features can significantly benefit projects of varying sizes and complexities. An all-round open-source test automation tool, Jest is indeed among the best out there, despite certain limitations.
Developers that enjoy customizing and harnessing tools to suit their requirements may face some stumbling blocks. However, the benefits of using Jest for JavaScript project testing far outweigh these hurdles.
Tags: #JavaScript, #Jest, #TestingFramework, #UnitTesting
[Reference Link](https://www.linkedin.com/pulse/pros-cons-different-test-tools-jest-craig-risi)