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.
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.
Strong documentation and support: As a testing framework that has been in existence since 2011 and was actively supported by Meta for most of its history, Jest has gained a large following. It features high-quality documentation and it's easy to find community support for working with Jest.
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.
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.
That said, Jest and Vitest may deliver somewhat different outcomes due to certain differences in how they work.
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.
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:
Running tests for projects developed with Vite.
Testing projects that require extensive numbers of tests, and/or where test speed is a priority.
On the other hand, Jest is ideal for the following use cases:
Projects where test speed is less of a priority.
Projects where access to extensive documentation and community support is important.
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.