Automated E2E testing is an invaluable asset if the underlying framework supports it. As the size of an app grows, automated E2E testing can save a lot of manual effort. Without automation it's just a never-ending battle to make sure the app is functional. However, remember that in an E2E setup, not everything is automatable; it may require a lot of effort to automate. With due diligence, we can offload a good amount of manual effort but not everything.
The process of E2E testing a web-based application is about running the application in a real browser and asserting the behavior of the application based on the user interface state. This is how an actual user does testing.
Browser automation holds the key here and modern browsers have become smarter and more capable in terms of supporting automation. Selenium tools for browser automation are the most popular option out there. Selenium has the WebDriver (http://www.w3.org/TR/2013/WD-webdriver-20130117/) API...