Enzyme VS jest

Probably Enzyme was the first to popularize component testing in React by doing shallow rendering and expecting some things to be there in the React component tree. Then React Testing library came and took component testing to a whole new level.

Enzyme is another popular testing utility for React. It allows you to manipulate and traverse React components' output, making it easier to write comprehensive tests.

ljharb is an extremely interesting person. There’s no doubting the positive impact he’s had on the OSS community and the work he’s done.

However, there are some things he does that are incomprehensible.

For example, Enzyme. Over three years ago this issue was opened for Enzyme on React 17: https://github.com/enzymejs/enzyme/issues/2429

Nothing moved for a while, and I think he said something along the lines of “if you want React 17 support, stop complaining and help”. So the community got involved. There are multiple PRs adding React 17 support. Many unofficial React 17 adapters. A lot of people have put a lot of work into this, ensuring compatibility, coverage etc. Yet to this day, none of them have been merged. Eg https://github.com/enzymejs/enzyme/pull/2564

Given the amount of time that has passed, and the work the community has put in, something is amiss. It feels like he’s now intentionally avoiding React 17+ support. But why? I don’t understand why someone would ask for help then ignore the help when it comes in. That isn’t much better than the swathe of rude/entitled comments he was getting on the issue before he locked it.

I ended up migrating to RTL, but this made many of my tests more complicated (especially compared to shallow rendering).

Enzyme Documentation

One way to do this is by writing tests for your React components. Tools like Jest and Enzyme make it easy to test your component's behavior, rendering output, and state changes. By writing tests for your components, you can ensure that they behave as expected and prevent issues before they reach production.

GitHub link: https://github.com/enzymejs/enzyme

So If you have experience with enzyme testing, where you might be checking the value of state once you click any button or you might be checking the prop value If something changes.

Enzyme offers two types of API for shallow rendering and full rendering. Both are preferred for different test scenarios and functionalities.

At Visa, I was writing unit tests for a Next.js project using components designed with Chakra UI. That's where React Testing Library came in handy. Unlike other solutions like Enzyme, I did not have to worry about the application snapshot but could instead focus on each UI element, its expected behaviour and the data it would render upon user interactions.

Superset uses Jest and React Testing Library (RTL) to write unit and integration tests. In the past we used Enzyme, but now that we're currently converting all of our class components to functional components, Enzyme cannot support our testing needs. Since RTL is better for testing functional components, we're converting all of our test files to RTL. This can be quite a learning curve - I've gone through a lot of the process so I'd like to share what I've learned so far.

GitHub | Website

Jest

you have selected a testing framework. In my case, it's Jest with Supertest

Jest, created and maintained by Facebook, is a JavaScript testing framework with a focus on simplicity. It is often recognized for its zero-configuration setup and seamless integration, especially with React applications, making it a favored choice for developers in both small-scale projects and large enterprise applications.

Jest (https://jestjs.io/)

console.error Jest encountered an unexpected token Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax. Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration. By default "node\_modules" folder is ignored by transformers. Here's what you can do: • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/ecmascript-modules for how to enable it. • If you are trying to use TypeScript, see https://jestjs.io/docs/getting-started#using-typescript • To have some of your "node\_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config. • If you need a custom transformation specify a "transform" option in your config. • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option. You'll find more details and examples of these config options in the docs: https://jestjs.io/docs/configuration For information about custom transformations, see: https://jestjs.io/docs/code-transformation

Note: I will be using Jest as testing framework throughout the examples.

We use Jest Framework for testing. Jest is not a dogma, and, of course, in its place can be any other test runner, such as Mocha or Ava. Let's focus on tests. I'll provide a short example because I don’t want to waste your time. You can find the full version here. It's crucial to read the comments in the code below. Let's go!

Jest has long been my favorite got to test runner when it comes to UI unit and integration testing. With tools like React Testing Library (Testing Library framework for React) you get the benefit of very easy to write and maintain tests, as well as a quick and efficient way to run our tests.

Jest is a well-regarded JavaScript testing framework primarily designed for React applications, although its utility extends to projects using Babel, JavaScript, Node, Angular, and Vue. Created by Facebook, Jest emphasizes ensuring the correctness of JavaScript codebases. It allows developers to write tests with a familiar, feature-rich API, making the testing process swift and enjoyable​​.