Intern is a new JavaScript testing stack developed by SitePen, which integrates seamlessly with Sauce Labs, a cloud testing company that uses the W3C's WebDriver standard. The project aims to provide high-quality, well-tested code for web applications, addressing limitations of existing testing tools like D.O.H. SitePen adopted features from existing products and added innovations based on their experience writing web apps and JavaScript libraries. Intern offers long-term interoperability and flexibility, making it an integral part of SitePen's development strategy, promoting the open-source way and available for others to use as well.