Argus Eyes
A lightweight commandline tool for visual regression testing of UI
...Argus eyes work by going over a straightforward JSON file containing the resolutions you want to capture, as well as the pages with theirs url's, and the components with their CSS-selectors. Once argus eyes know where to find the components, it's time for some command line action. The first command you want to use is $ argus-eyes capture master. This makes argus eyes go over the config file and take screenshots of all specified components in there. The screenshots are saved in .argus-eyes/master and this set of screenshots can be compared with another set.