What is Jest?
Who uses Jest?
Here are some stack decisions, common use cases and reviews by companies and developers who chose Jest in their tech stack.
I'm working as one of the engineering leads in RunaHR. As our platform is a Saas, we thought It'd be good to have an API (We chose Ruby and Rails for this) and a SPA (built with React and Redux ) connected. We started the SPA with Create React App since It's pretty easy to start.
We use Jest as the testing framework and react-testing-library to test React components. In Rails we make tests using RSpec.
Our main database is PostgreSQL, but we also use MongoDB to store some type of data. We started to use Redis for cache and other time sensitive operations.
We have a couple of extra projects: One is an Employee app built with React Native and the other is an internal back office dashboard built with Next.js for the client and Python in the backend side.
Our whole Vue.js frontend stack (incl. SSR) consists of the following tools:
- Vue Styleguidist as our style guide and pool of developed Vue.js components
- Vuetify as Material Component Framework (for fast app development)
- TypeScript as programming language
- Apollo / GraphQL (incl. GraphiQL) for data access layer (https://apollo.vuejs.org/)
- ESLint, TSLint and Prettier for coding style and code analyzes
- Jest as testing framework
- Google Fonts and Font Awesome for typography and icon toolkit
- NativeScript-Vue for mobile development
The main reason we have chosen Vue.js over React and AngularJS is related to the following artifacts:
- Empowered HTML. Vue.js has many similar approaches with Angular. This helps to optimize HTML blocks handling with the use of different components.
- Detailed documentation. Vue.js has very good documentation which can fasten learning curve for developers.
- Adaptability. It provides a rapid switching period from other frameworks. It has similarities with Angular and React in terms of design and architecture.
- Awesome integration. Vue.js can be used for both building single-page applications and more difficult web interfaces of apps. Smaller interactive parts can be easily integrated into the existing infrastructure with no negative effect on the entire system.
- Large scaling. Vue.js can help to develop pretty large reusable templates.
- Tiny size. Vue.js weights around 20KB keeping its speed and flexibility. It allows reaching much better performance in comparison to other frameworks.
We are in the process of adopting Next.js as our React framework and using Storybook to help build our React components in isolation. This new part of our frontend is written in TypeScript, and we use Emotion for CSS/styling. For delivering data, we use GraphQL and Apollo. Jest, Percy, and Cypress are used for testing.
We chose Vue.js at Codecov to replace a front end that was based mostly on server side rendered Python templates, and was getting fairly long in the tooth. The move to Vue.js allowed us to take a more component driven approach to our front end, providing greater flexibility and reuse when creating new pages and refactoring old ones. Another bonus was how easily we could integrate Axios with VueJS for making AJAX calls within Vue.js components and their associated vuex stores. We were also able to easily integrate Vue.js with the Jest testing framework, which allowed to provide test coverage for a front end where none previously existed.
The move to Vue.js has allowed us to be more agile in our front end development by further decoupling our front end from our back end. Additionally, by fully embracing a component-driven approach, we're able to more easily isolate and test functionality, leading to a more readible, maintainable, and extensible front end codebase.
Choosing redux-saga for my async Redux.js middleware, for a React application, instead of the typical redux-thunk .
Redux-saga is much easier to test than Redux-thunk - it requires no module mocking at all. Converting from redux-thunk to redux-saga is easy enough, as you are only refactoring the action creators - not your redux store or your react components. I've linked a github repo that shows the same solution with both, including Jest tests.
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.
- 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