What Karate UI is for

The purpose of end-to-end (E2E) testing starting with the UI is to get a full picture of the application from the frontend—including JavaScript and CSS frameworks, cookie handling, and so on—all the way to the backend with its microservices, data storage, caches, and APIs.

This kind of testing is usually much slower and more error prone than pure API testing but at the same time, it paints a better picture of the state of the application. Consider this: if one API does not function properly, that does not necessarily mean that the functionality of the web application is restricted. If a full browser-based E2E test has a legitimate failure, the application is likely unusable.

There are many different browser testing tools available in today’s market. One of the oldest and most well-known is Selenium (https://www.selenium.dev). This project established the W3C WebDriver protocol, which is used to automate interactions with web browsers...