Selenium - Selenium automates browsers. That's it! What you do with that power is entirely up to you. Primarily, it is for automating web applications for testing purposes, but is certainly not limited to just that.
sitebot.ai - The easiest way to monitor that your website is working as it should. Sitebot uses a real browser to test your site and login automatically.
DalekJS - DalekJS is an open source UI testing tool.
Ghost Inspector - Easily create automated browser tests for your websites and web apps. Ensure everything works and looks the way it should. No coding required. 14 day free trial!
Webinject - WebInject is a free tool for automated testing of web applications and web services.
DiffHub - Automated Web UI & Functional Testing for non Engineers