Table of Contents

• Why writing tests?
• What type of tests should we choose?
• Write and debug your tests faster with Jest Preview/ Vitest Preview
• Some thoughts on Open Source

Why writing tests?

• Catching bugs early

• Confident when add new features

• Confident when refactor code

• Save time in the long run

=> It’s like an investment

Why engineers don’t usually write tests?

• Boring tasks

• No immediate value

• Low ROI in a short term

• Hard to debug

What type of tests should we choose?

https://kentcdodds.com/blog/the-testing-trophy-and-testing-classifications

What type of tests should we choose?

Unit tests

What type of tests should we choose?

E2E tests

What type of tests should we choose?

Integration tests with "e2e" style

Write and debug your tests faster with Jest Preview/ Vitest Preview

What is Jest Preview and why I built it?

Problem:

• When you run a test, you only see the result in the terminal

• You don’t know what your app looks like when the test is running

• It’s very hard to debug a failed test: Very Longgg HTML

Have you ever tried to click on a button, but there is no button, it's just the spinner is loading?

=> Question: If jest can print out the HTML, can we render it on a browser?

=> Yes. We can!!

What is Jest Preview and why I built it?

What is Jest Preview and why I built it?

Benefits of Jest Preview

• Debug a failed test easier

• We can see what our app looks like, so the next testing steps are easily predictable => write test faster

• Shorten the gap between unit/ integration tests and e2e tests, but still fast in execution time

=> My personal experience: I write tests 200-300% faster, thanks to jest-preview

What did I receive from doing open source software?

• Knowledge. A lot of knowledge.

• Read open source code a lot => code reading/ debugging skills improved

• Understand how the tools you use everyday work under the hood => Better programmer

• Rabbit hole: Jest, Vite core, CRA core, Websocket, chokidar, shebang, PostCSS, Babel…

What did I receive from doing open source software?

• Opportunities:

• Nominated for the Most Exciting Use of Technology, React Open Source Awards, React Summit

• Jobs: Companies reach out

• Conferences/ Tech events

What did I receive from doing open source software?

Know great developers:

• Twitter

What did I receive from doing open source software?

Know great developers:

• In-person (CityJS Singapore 2022)

What did I receive from doing open source software?

Know great developers:

• In-person (JSConf Korea 2022)

What did I receive from doing open source software?

I received a lot of thanks: