Craft 2023 - Lucas Fernandes da Costa
Lucas Fernandes da Costa
Founder, engineer, and published author at ergomake
About Lucas Fernandes da Costa

I’m a software engineer, published author, and professional problem-solver whose preference for tea was developed during my 5 years living in London.

I write JavaScript most of the time and am passionate about open-source. For the past few years, I have been a maintainer of Chai.js and Sinon.js, two of the most popular testing libraries in the JS ecosystem. I’m highly active on GitHub and have contributed to numerous projects, including Jest and NodeSchool.

As an author, I’ve written Testing JavaScript Applications, a book published by Manning Publications.

My blog (, which features some of my best writing, is often on HackerNews’ front page. Some of its content is used by universities, like the Vancouver Island University, and online courses, such as the Boucoup Modern & Future JavaScript Course, as reference material.

I have been voluntarily translated into many languages, including Russian, Mandarin, French, Portuguese, and Spanish.

As a speaker, I have presented talks in more than ten countries. I’ve spoken at events such as O’Reilly’s Fluent Conf in San Jose - CA, JSConf Colombia, HolyJS (both in Moscow and St. Petersburg), NebraskaJS, TheConf São Paulo, DevFest Nantes, FrontEnd United Utrecht, CityJSConf London and many others.

I’m always trying to find better and more efficient ways to solve problems. “Strive to be lazy” this is my motto.