Happo.io vs Poltergeist: What are the differences?
Developers describe Happo.io as "Cross-platform, cross-browser screenshot testing for modern user interfaces". Happo is a visual regression testing tool. It hooks into your CI environment to compare the visual appearance of UI components before and after a change. Screenshots are taken in different browsers and across different screen sizes to ensure consistent cross-browser and responsive styling of your application. On the other hand, Poltergeist is detailed as "A PhantomJS driver for Capybara". Poltergeist is a driver for Capybara. It allows you to run your Capybara tests on a headless WebKit browser, provided by PhantomJS.
Happo.io and Poltergeist can be primarily classified as "Testing Frameworks" tools.
Poltergeist is an open source tool with 2.53K GitHub stars and 437 GitHub forks. Here's a link to Poltergeist's open source repository on GitHub.