Overview

Jest

Stacks15.2K

Followers4.1K

Votes175

Chai

Stacks5.4K

Followers196

Votes0

GitHub Stars8.3K

Forks707

Chai vs Jest: What are the differences?

Chai and Jest are both popular JavaScript testing frameworks used for writing unit tests. Let's explore the key differences between them.

Syntax: Chai allows developers to choose from multiple assertion styles, including Should, Expect, and Assert, giving them flexibility in writing assertions in a way that feels comfortable. On the other hand, Jest has a built-in expectation library, using a more opinionated syntax where assertions are written with the "expect" keyword.
Mocks and Spies: In Chai, developers need to use separate libraries like Sinon or Testdouble to create mocks and spies for stubbing or spying on function calls and verification purposes. However, Jest has built-in functions like "jest.spyOn" and "jest.fn" that can be used directly without any external dependencies, providing a more seamless mocking and spying experience.
Configuration: Chai does not come with a built-in test runner or configuration. Developers have the freedom to choose their preferred test runner (e.g., Mocha, Jasmine) and configure it as per their needs. In contrast, Jest provides a fully-featured test runner and configuration out of the box, reducing setup time and the need for additional configurations.
Performance: Chai can be slower compared to Jest for larger test suites due to its assertion style flexibility and need for external libraries for functionalities like mocking and spying. Jest, on the other hand, is designed to prioritize performance, utilizing parallelism and smart test skipping techniques, resulting in faster running tests.
Snapshot Testing: Jest has built-in support for snapshot testing, allowing developers to capture the rendered output of components and compare it with the stored snapshot to detect any unintended changes. Chai does not have native support for snapshot testing, requiring developers to use extra libraries like Chai-enzyme or Enzyme to achieve similar functionality.
Test Coverage Analysis: Jest provides built-in tools for generating code coverage reports, making it easier for developers to track the amount of code covered by their tests. Chai itself does not have native support for code coverage analysis, requiring integration with additional tools or libraries to achieve the same level of coverage tracking.

In summary, Chai provides flexibility in assertion style and allows developers to choose their preferred test runner, whereas Jest offers a more opinionated syntax and comes with a built-in test runner along with features like snapshot testing and code coverage analysis.

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Advice on Jest, Chai

Dane

Feb 7, 2020

Needs adviceon

Cypress

Jest

As we all know testing is an important part of any application. To assist with our testing we are going to use both Cypress and Jest. We feel these tools complement each other and will help us get good coverage of our code. We will use Cypress for our end to end testing as we've found it quite user friendly. Jest will be used for our unit tests because we've seen how many larger companies use it with great success.

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Anonymous

Feb 6, 2020

Needs advice

Postman will be used to do integration testing with the backend API we create. It offers a clean interface to create many requests, and you can even organize these requests into collections. It helps to test the backend API first to make sure it's working before using it in the front-end. Jest can also be used for testing and is already embedded into React. Not only does it offer unit testing support in javascript, it can also do snapshot testing for the front-end to make sure components are rendering correctly. Enzyme is complementary to Jest and offers more functions such as shallow rendering. UnitTest will be used for Python testing as it is simple, has a lot of functionality and already built in with python. Sentry will be used for keeping track of errors as it is also easily integratable with Heroku because they offer it as an add-on. LogDNA will be used for tracking logs which are not errors and is also a Heroku add-on. Its good to have a separate service to record logs, monitor, track and even fix errors in real-time so our application can run more smoothly.

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Comments

Detailed Comparison

Jest	Chai
Jest provides you with multiple layers on top of Jasmine.	It is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework. It has several interfaces that allow the developer to choose the most comfortable. The chain-capable BDD styles provide an expressive language & readable style, while the TDD assert style provides a more classical feel.
Familiar Approach: Built on top of the Jasmine test framework, using familiar expect(value).toBe(other) assertions;Mock by Default: Automatically mocks CommonJS modules returned by require(), making most existing code testable;Short Feedback Loop: DOM APIs are mocked and tests run in parallel via a small node.js command line utility	-
Statistics
GitHub Stars -	GitHub Stars 8.3K
GitHub Forks -	GitHub Forks 707
Stacks 15.2K	Stacks 5.4K
Followers 4.1K	Followers 196
Votes 175	Votes 0
Pros & Cons
Pros 36 Open source 32 Mock by default makes testing much simpler 23 Testing React Native Apps 20 Parallel test running 16 Fast Cons 4 Documentation 4 Ambiguous configuration 3 Difficult 2 Ambiguous 2 Multiple error messages for same error	No community feedback yet

What are some alternatives to Jest, Chai?

Mocha

Mocha is a feature-rich JavaScript test framework running on node.js and the browser, making asynchronous testing simple and fun. Mocha tests run serially, allowing for flexible and accurate reporting, while mapping uncaught exceptions to the correct test cases.

Jasmine

Jasmine is a Behavior Driven Development testing framework for JavaScript. It does not rely on browsers, DOM, or any JavaScript framework. Thus it's suited for websites, Node.js projects, or anywhere that JavaScript can run.

Cypress

Cypress is a front end automated testing application created for the modern web. Cypress is built on a new architecture and runs in the same run-loop as the application being tested. As a result Cypress provides better, faster, and more reliable testing for anything that runs in a browser. Cypress works on any front-end framework or website.

CodeceptJS

It is a modern end to end testing framework with a special BDD-style syntax. The test is written as a linear scenario of user's action on a site. Each test is described inside a Scenario function with I object passed into it.

Protractor

Protractor is an end-to-end test framework for Angular and AngularJS applications. Protractor runs tests against your application running in a real browser, interacting with it as a user would.

AVA

Even though JavaScript is single-threaded, IO in Node.js can happen in parallel due to its async nature. AVA takes advantage of this and runs your tests concurrently, which is especially beneficial for IO heavy tests. In addition, test files are run in parallel as separate processes, giving you even better performance and an isolated environment for each test file.

Ghost Inspector

It lets you create and manage UI tests that check specific functionality in your website or application. We execute these automated browser tests continuously from the cloud and alert you if anything breaks.

QUnit

QUnit is a powerful, easy-to-use JavaScript unit testing framework. It's used by the jQuery, jQuery UI and jQuery Mobile projects and is capable of testing any generic JavaScript code, including itself!