I didn't got into GUI testing and I saw a major interest on that. So I decided to take a look at the current state of GUI testing. Here are the main tools that I came up with:
I got very frustrated while trying to test AJAX powered pages. For SPA apps, Zombie wouldn't be an ideal solution.
Casper on the other hand, is a wrapper around Phantom.js which utilises a Webkit headless browser and will do a full rendering of your web page in order to test it. Since you will have a full representation of your site you can even take screenshots for easier QA.
Casper.js has neat documentation and it's API is really easy to follow and adopt.
Now, on the heavy side, we have Selenium. Selenium is a set of projects. It started off by auto running browsers and injecting code into them so we can test it. Since then, browsers vendors kept evolving and expose a full set of control over their browsers so Selenium has native support over those, with the Selenium WebDriver.
You will have to install all the browsers you need to test locally and then use Selenium to run tests on them. It's pretty basic.
Selenium's internals and configuration is a bit overcomplicated and if you don't need it, you don't have to get into it. Nightwatch is a great layer of abstraction on top of Selenium that will do all the heavy work for you.
I am sure there are tone of other solutions out there. Although, you will have to do a research on your own before starting your GUI testing journey, at then end just pick one and start.
Are you using something already? What's that?