React: Building Modern Web Applications

Jest – BDD unit testing from Facebook

Jest is a JavaScript unit testing framework intended to support behavior-driven development. It is built on top of Jasmine, and in the future, it may be able to interact with other foundations. It has been used for a couple of years and is used on Facebook, though there appears to be no decisive endorsement that ReactJS development is best done using Jest. (Facebook uses JSX with ReactJS internally but tends to make a relatively unopinionated statement that about half of ReactJS users opt to use JSX. It is actually designed to be entirely optional.)

Note

JSX—the X boldly meaning XML at a time when XML has fallen out of favor—is a well-made syntactic sugar that "puts angle brackets in your code." This loosely ...