Selenium is a popular browser automation framework. There's a good introduction and examples here. Let's see how to use it in NetBeans IDE, for Java applications, without installing plugins.
In the upcoming NetBeans IDE 8.1 (already available as development builds), create your Maven Java EE project, which will give you this:
In the New File dialog, you'll find Selenium test files:
When you select the Selenium Test Case above and click Next and complete the wizard, you'll have the new Selenium test file, as well as all the dependencies you'll need (click to enlarge the image below):
Right-click the application, choose test file, the rest runs, the browser opens, and the results are shown in the Test Results window.