TestRigor is a testing tool that uniquely identifies new functionalities in applications by focusing on changes rather than every line of code, allowing developers to pinpoint the source of new bugs. It offers a dynamic testing experience by executing actions similar to those of a user, such as clicking buttons and filling forms, while tracking previous test results. In a demonstration with a simple calculator app, TestRigor effectively detects and reports new functionalities, like the addition of a button, and provides descriptive reports with screenshots that highlight changes and actions taken. This capability enables developers to easily locate and address new features using identifiers like HTML IDs. Users are encouraged to explore TestRigor by signing up or requesting a demo to experience its practical application in their projects.