WATIR stands for "Web Application Testing in Ruby". Watir is a free, open-source functional testing tool for automating browser-based tests of web applications. It is pronounced water. Watir drives the Internet Explorer browser the same way people do. It clicks links, fills in forms, presses buttons. Watir also checks results, such as whether expected text appears on the page.
Watir is a Ruby library that works with Internet Explorer on Windows. Like other powerful programming languages, Ruby gives you the power to connect to databases, read data files, export XML and structure your code into reusable libraries.