Personal playground for explaining how I understand the writing of unit (and maybe even more) tests. Mainly using Jest and React Testing Library 🚀.

Motivation behind this mini project is that I often do not know HOW to test things in the code which I write. Do not get me wrong, I can write the test suites and case from syntax point of view and I can also get around things like coverage percentage. The main point is that more often than not I am not sure if I am testing the right things or if I am testing those things correctly. The goal of this is to have a quick notebook in my hand where can I have a look to reming myself if I am doing the right thing.

This "notebook" is written for React but ultimately all of principles and stuff should be applicable in different languages and different contexts.

This little experiment will be using new Yarn version so I (and maybe others in the future) can leverage the PnP system that it offers. Repository will be divided into multiple packages and each will be generated using ViteJS. The testing itself will be done using Jest and Testing Library.

The original idea was to use PnP system of Yarn Berry version I could not set up testing-library and Jest together with Typescript. After some investigation and multiple trials I decided to fall back to the classic CRA. After I finish all the cases I plan to debug the problems with Yarn Berry version more.

Each package will focus on comperehensive area or context which I encountered during my development time. Each area or context will have separate README.md file where I will try to explain (to myself) how I am testing stuff and why I am doing it in such way.

For now those are gonna be:

• Basic React components
• "Business" logic
• API client instance (Axios, Fetch)
• Component visuals and changes based on some logic

Later I am thinking about following:

• Redux (actions, reducers, middlewares)
• Cypress E2E tests
• Cypress visual diff