Vitest vs. Jest: Differences, Benefits, and Challenges

If you develop applications with JavaScript, you have plenty of choices when it comes to solutions for testing your code. Among the most popular are Jest and Vitest.

Which testing framework – Jest or Vitest – is better? The answer depends on factors like how you manage modules within your JavaScript code, what your development environment looks like, and how much priority you place on the speed of test execution.

Keep reading for a breakdown of the differences between Jest vs. Vitest, along with guidance on how to decide which testing framework will work best for your JavaScript testing needs.

Jest is a testing framework for JavaScript. It supports most of the popular JavaScript frameworks, such as Vue, Angular, React, and Node.

Jest is built on top of Jasmine, another JavaScript testing framework. However, Jest provides some features that are not present in Jasmine, such as native support for mocking.

Jest is also different from Jasmine in that Jest originated at Meta (the company formerly known as Facebook), whereas Jasmine is an open source project that is not closely associated with any specific company or group. That said, Meta transitioned Jest to an open source project directed by the OpenJS Foundation in 2022, so there is no longer a major difference between Jasmine and Jest in terms of how the projects behind them are organized.

It would be an overstatement to say that Jest is truly unique. It's quite similar in overall design and usage to other JavaScript testing frameworks, including Vitest.

Still, Jest does stand out in certain respects.

Jest's most notable features include built-in support for mocking, which allows developers to run simulated tests against objects that don't exist within a given test scope. Jest also offers a snapshot feature, which is useful if you want to compare the output of two different tests, and it supports parallel testing, which can dramatically reduce the time it takes to complete a set of tests. In addition, Jest allows you to run tests with minimal setup or configuration.

These features aren't entirely unique to Jest, but they do distinguish Jest from many other JavaScript testing frameworks.

The most important benefits of using Jest for JavaScript testing include:

In short, if you're looking for a simple JavaScript testing framework that also provides access to some advanced features, such as easy implementation of mocking, Jest is a good solution.

Vitest is a JavaScript unit testing framework. It was created to complement Vite, a tool for helping to manage and build JavaScript-based Web applications.

It's possible to use Vitest without Vite, but doing so will typically require more effort on the part of developers to configure tests. If you use Vitest to test code that you manage through Vite, most of the testing setup will happen automatically, thanks to the tight integration between Vitest and Vite.

Vitest is compatible with most of the Jest API. That means that most tests developed for Jest can also be executed using Vitest, with few if any changes needed.

Vitest is similar to Jest in that it provides virtually all of the features and functionality that you'd expect from a modern testing framework. But its main distinguishing characteristic is speed and (when used in conjunction with Vite) simplicity.

Let's look at Vitest's benefits in a little more detail.

Vite means fast in French, and Vite and Vitest were named accordingly. As a testing framework, Vitest's most important feature is its focus on speed.

The performance of tests run with Vitest will vary depending on what you're actually testing, of course. But as a basic benchmark, consider this comparison of Jest vs. Vitest testing times from dev.to, which found that some Vitest tests ran more than 4 times faster than tests with Jest.

The main advantage of Vitest for JavaScript testing, then, is speed. For many testing scenarios, Vitest is likely to result in the fastest overall test routines of any modern JavaScript testing framework (although again, your results may vary depending on exactly what you're testing, so it's worth experimenting with different frameworks rather than assuming Vitest will always be faster).

Another advantage of Vitest is its tight integration with Vite, which enables a simple test setup and management experience. If you manage your application code through Vite, you can reuse most of the configurations, plugins, and other elements you've already developed when you create your tests.

Whether you choose Jest or Vitest for JavaScript testing, you can expect a modern, simple, and fast testing experience. Both frameworks are mature, compatible with all of today's popular JavaScript development frameworks, and designed with efficiency in mind. They can also both serve as the foundation for a test automation strategy.

That said, Jest and Vitest may deliver somewhat different outcomes due to certain differences in how they work.

Again, Jest and Vitest both support testing of JavaScript code written using almost any modern framework. If you code in JavaScript, you can probably test your code equally effectively using either Jest or Vitest.

That said, the fact that Vitest is tightly coupled with Vite means that it makes most sense to use Vitest if you're also using Vite (although, again, it's possible to use Vitest without using Vite). In contrast, Jest is more agnostic with regard to the development tooling you're using.

Although there may be some situations where Jest tests run faster than Vite tests, if you had to place a bet on which framework will result in faster tests, Vitest would be the much safer option. 

Whether Vitest's speed advantages compared to Jest are actually a key consideration for you, however, depends on how many tests you are running and where you are running them. If you're running a large number of tests on a local development box with limited resources, you probably care more about fast test speed than you do if you're running only a handful of tests, or if you're running tests on infrastructure with plenty of resources available.

One of the nuanced, but potentially important, differences between Jest and Vitest is the module management systems they support by default.

In JavaScript, there are multiple ways to manage modules. A popular traditional approach was to use CommonJS. Jest is designed to work with CommonJS.

In contrast, Vitest was designed to be compatible with ECMAScript Modules, or ESM, a more modern approach to working with JavaScript modules.

What this means from a testing standpoint is that the way you manage modules for your JavaScript project could be a factor in choosing between Jest vs. Vitest. If you're using CommonJS, testing with Jest will be simpler because Jest will integrate nicely with your modules. But if you use ESM, Vitest is the more obvious choice.

Jest was released a decade before Vitest appeared, and a larger community has grown up surrounding Jest. As a result, it's easier, in general, to find documentation and support for Jest.

This may change over time; Vitest currently enjoys a lot of popularity, and it may well end up with just as strong a community around it as Jest. But for the time being, Jest benefits from a better established ecosystem than Vitest.

To sum up, key use cases for Vitest include:

On the other hand, Jest is ideal for the following use cases:

While there are important differences between Jest and Vitest, it's worth keeping in mind that both frameworks are excellent. If you truly can't decide which one is best for you, it's likely that the differences don't actually matter too much.

And using the Sauce Labs platform, you can test with Jest, Vitest, and a wide array of other modern testing frameworks – so you don't need to commit to one framework or another in order to take advantage of scalable, high-performing test infrastructure for virtually any testing need.