How do you test CSS? Being a declarative language, when you say you want a heading to be blue, it is simple as writing h1 { color: blue }
. But, even if changes that you make to your stylesheets may seem innocuous, they may lead to unintended, far-reaching consequences. This site has built up a collection of resources on best practices for testing CSS; from image diffing, to syntax linting. Definitely a great starting point for any front end developer.