Take a look at this snippet taken directly from the official GitHub repo:
If you’re into name-dropping, Intern gets used every day by teams at Twitter, Stripe, Mozilla, IBM, Marriott, Philips, Zenput, Alfresco, Esri, HSBC, ING, Intuit, and more. It’s also the testing framework of choice for growing numbers of open-source projects.
You can run tests straight in your browser or via Node.js. Intern is very flexible and it’s perfect for intermediate-to-advanced developers who know how to work the tool.
Just like any other library, Intern requires a bit of research to fully comprehend.