Testing Frameworks: Jest vs Vitest

With testing frameworks, developers can run code tests to ensure correct functionality and meet requirements. 

Yet, with the amount of resources, it can be challenging to choose the right testing framework for your project.

This blog post will compare two of the most used testing frameworks: Jest and Vitest. 

Let's dive into the two of them so that next time, you can choose wisely!

What is a Testing Framework?

A testing framework is a tool designed to ease testing for developers.

Some use cases include help writing and running test cases, as well as generating reports.

This procedure ensures that all parts of the code are tested, minimizing the chance of undiscovered bugs.

By automating tests, developers can run code more frequently and catch errors early on.

As a result, they can reduce the cost and effort required to fix them later. 

Testing frameworks also enable faster cycles and more reliable software.

They’re a further standardized approach to testing, facilitating collaboration and test case sharing.

These practices promote code quality and consistency across teams, ensuring everyone is on the same page regarding best practices.

Features of Testing Frameworks

• Easy Setup. Testing frameworks should have a simple setup process so that developers can start writing tests immediately.
• Strong Assertions. Frameworks must offer ways to check that the code behaves as expected and to compare expected and actual results.
• Mocking. Creating mock versions of external dependencies can isolate code and test specific functions.
• Test Coverage. Frameworks should generate useful reports so that developers can find areas that need more testing.

What is Jest?

Jest is a widely used testing framework, focused on simplicity and ease of use and developed by Facebook.

This open-source testing framework uses JavaScript's ability to mock functions and handle asynchronous code.

With Jest, developers can write efficient and maintainable tests.

Jest offers features like running complex tests in parallel, which improves execution times. 

Another impressive feature of Jest is its seamless integration with JS libraries and frameworks like React.

Jest Core Features

• Zero Configuration. Jest requires minimal configuration, making setting up and writing tests effortless. Devs can focus on writing tests instead of spending time with coverage on complex setup processes.
• Snapshot Testing. With Jest, teams can easily create and compare snapshots of their components, ensuring consistent rendering. This feature allows for easy detection of unintended changes in the User Interface (UI).
• Code Coverage. Jest provides detailed code coverage reports, highlighting areas requiring additional testing. It identifies gaps in test suites and ensures that all parts of codebases are thoroughly tested.
• Mocking Capabilities. Jest offers built-in support for mocking, allowing devs to replace external dependencies with mocked versions for isolated testing. This feature enables developers to test their code in isolation without worrying about the behavior of external dependencies.

Pros and Cons of Jest

Pros of Jest

• Intuitive. You can write your tests using the expect and describe functions and use matchers to verify the results. Jest also has a rich set of assertions and utilities, such as asynchronous operations, exceptions, timers, and promises.
• Performance. Jest runs tests in parallel and isolates them from each other, which reduces the chances of interference and flakiness. Jest also uses a caching system that optimizes the test execution and avoids unnecessary work. 
• Integrations. Its seamless integration with React and other JavaScript testing libraries makes it popular for testing JavaScript applications.

Cons of Jest

• Memory Footprint. Jest’s parallel component testing and caching features come at the cost of high CPU and RAM usage.
• Debugging. Jest doesn’t have a built-in debugger, relying on external tools like Node Inspector or Chrome DevTools to debug. It also does not have good support for source maps, making it hard to trace errors and stack traces back.
• Performance. While Jest performs well for small and medium-sized test suites, its performance may decrease when handling larger ones.

What is Vitest?

Vitest is a testing framework focused on unit tests, integration tests and component tests.

These features simplify and speed up the testing process for JavaScript code. 

It was created by Evan You, the creator of the Vue framework, and it was inspired by Jest.

Vitest uses Vite as its core infrastructure, which means it can take advantage of Vite’s features.

Vitest supports Behavior-Driven (BDD) and Test-Driven Development (TDD), allowing developers to choose the best approach.

One of the key advantages of Vitest is its integration with various Continuous Integration (CI) tools. 

These integrations ensure that every code change is thoroughly tested before deployment.

Whether you use Jenkins, Travis CI, or any other CI tool, Vitest covers you!

Vitest Core Features

• Extensibility. Vitest's modular architecture allows developers to extend its functionality using custom plugins and extensions. You can tailor Vitest to suit your testing, making it highly flexible and customizable.
• Language Support. It supports a wide range of languages, enabling testing code written in different languages within a single framework. It has tools to test JavaScript, Python and Java code, among others. Additionally, it was designed with a Jest-compatible API to make migrations from Jest easier.
• IDEs Integration. This framework integrates with popular Integrated Development Environments (IDEs) like Visual Studio Code, Eclipse and IntelliJ IDEA, enhancing developers' productivity. Vitest's IDE integration allows you to run tests directly from your development environment.

Pros and Cons of Vitest

Pros of Vitest

• Speed. Vitest uses Vite's instant HMR and ESBuild bundler, facilitating module management. Some projects have reported faster test execution with Vitest than with other testing frameworks, making it a compelling alternative.
• Setup. Vitest setup reuses Vite’s config and plugins. You don’t have to worry about setting up Babel, webpack, or other tools to test your code. It also supports out-of-the-box ESM, TypeScript, JSX, and other modern features so that you can write your tests the same way as your code.
• Compatibility. Vitest aligns with the latest JavaScript development frameworks, practices, and ecosystem libraries, such as ES modules, TypeScript, and Vite. Vitest also supports Jest’s API, such as expect, snapshot, coverage, and more.

Cons of Vitest

• Documentation. Vitest’s documentation is still under development, so it may not cover all features, options or scenarios. Vitest’s documentation may also be outdated or inaccurate as the project evolves rapidly.
• Dependence. Vitest requires Vite as a dependency and works best with projects that use Vite. It’s not yet stable or production-ready and may not support some features or edge cases that Jest or other frameworks do.
• Community. Its community is still small and growing, so it may not have as many resources, tutorials, examples or plugins.

Vitest vs Jest Testing Frameworks

Now that we've explored the individual features of Jest and Vitest, let's compare them head to head.

Jest vs Vitest Performance

Jest and Vitest are both great options! 

Jest is particularly efficient when executing tests, thanks to its ability to run tests in parallel.

It can handle large-scale test suites quickly and effectively by distributing test cases across multiple threads.

As a result, Jest can complete the test suite in a fraction of the time compared to other testing frameworks.

On the other hand, Vitest's modular architecture allows developers to customize and optimize the testing environment.

With Vitest, developers can break the testing process into smaller, manageable modules.

This structure enables them to fine-tune the testing setup for optimal performance. 

Jest vs Vitest Ease of Use

Regarding ease of use, Jest shines with its zero-configuration setup and intuitive API.

Teams can quickly start writing tests without the need for extensive configuration.

Jest's zero-configuration setup eliminates the need to spend time configuring test runners, frameworks and other testing dependencies. 

Regarding Vitest setup, its flexibility and extensive documentation can make it more user-friendly.

Vitest provides various configuration options, allowing devs to tailor the testing environment to specific project requirements.

Jest vs Vitest Community and Support

Both Jest and Vitest boast active communities and provide extensive documentation and resources.

Since it’s backed by Facebook (Meta), it can ensure ongoing support.

The Jest community offers a wealth of knowledge and resources.

You can find online forums, tutorials, and plug-ins developed by community members.

This community ensures that devs can access timely support and collaborate with others to solve challenges.

As an open-source project, Vitest benefits more from community contributions and continuous improvement.

This nature encourages Vitest teams to contribute to its development, share their experiences and help each other.

Conclusion

Jest is ideal for projects that require robust and more stable ecosystems.

Vitest's flexibility and language-agnostic approach make it an ideal choice for new and modern projects. 

The choice between Jest and Vitest will depend on your project and your team's specific needs and preferences.

‍Get in touch with Capicua to learn more about what framework can do best for your requirements!