huddleeng/phantomcss

PhantomCSS is a tool for catching unintended visual changes in a website's appearance. The idea is straightforward: it takes a screenshot of a page or a specific part of a page, saves that as the approved "baseline" image, and then on every future test run it takes a new screenshot and compares the two. If anything looks different, it flags the failure and produces a highlighted image showing exactly where the change occurred, with altered pixels marked in a bright color so you can see at a glance what shifted. The project was built on top of two other tools: CasperJS, which controls a headless web browser to load pages and click through interactions, and Resemble.js, which does the pixel-by-pixel image comparison. Together they let a developer write a short script that opens a URL, performs some actions like clicking a button, takes a screenshot of the result, and then compares that screenshot against the stored baseline. If a CSS change accidentally moves a button or changes a font size, the test will catch it. This approach only works reliably on predictable, static content. The README notes that pages with moving parts or data that changes on each load (like timestamps or animations) will produce false failures unless you hide those elements during the test run. Setup involves installing PhantomCSS via npm or cloning the repository, then writing test files in JavaScript using the CasperJS API. The README includes a walkthrough demo: run the test suite once to generate baseline images, then make a visual change to the demo HTML file, run again, and observe the failure report with diff images. Important to note: the project was officially declared unmaintained in December 2017. The README states that the authors moved on and the project will receive no further updates. It may still work for simple use cases, but it relies on PhantomJS, which is itself no longer actively developed.