The following is a guest post by Jon Bellah, an Engineering Manager at 10up. Jon reached out to us about writing on the idea of visual regression testing, which is a form of CSS testing (i.e. making sure you don’t screw up your site by accident). I thought the use-case was particularly interesting: re-architecting CSS (converting to Sass, splitting up files, etc) and making sure there wasn’t regressions during that process. Here Jon will go into all that as well as some of the challenges of visual testing (e.g. changing content changes visual result) with clever workarounds.

Inheriting a codebase from new client is one of the most common, and most difficult, challenges I