Jest is a new javascript testing tool announced today. I thought I'd take it out for a spin testing the UI of a simple vanilla JS app - no CommonJS modules, no fancy stuff. Just old school JavaScript. Granted, it's probably not what the tool was optimized to do, but it totally worked.
The thing about Jest is that it mocks everything. Which is priceless for unit testing. But it also means you need to declare when you don't want something mocked.