Visual Regression Testing

Have you ever heard the one about the web developer who goes in to make one last change to the site at 4:45PM on a Friday afternoon? It is SUCH an easy fix--he can get it done and go home for the weekend with his head held high. Ah, what a relaxing weekend it will be!

Lots of stuff has been changing in Drupal 8 recently. In 8.3.0, a new experimental "layout discovery" module was added to core, which conflicted with the contrib "layout plugin" module.