It's a language. Oracle owns it, and it works well for many things.
Unit testing. The original Java unit testing tool. It's pretty great.
Great for mocking classes.
Use this to mock those pesky, hard-to-mock static classes.
The Java IDE. (Other people have other preferences, but this one is mine.)
Code coverage tool.
Automatically run tests when you save updates in Eclipse (or other supported Java IDE).
Mocha is a feature-rich JavaScript test framework running on node.js and the browser.
Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework.
An example Gruntfile for running Mocha + Chai tests.