There are several tools available for unit testing JavaScript code, including in-browser frameworks like YUI Test and QUnit, headless frameworks like JSpec that can run tests without a browser, and hybrid approaches like JsTestDriver that execute tests in browsers but allow controlling and viewing results from the command line or IDEs. These tools help debug code, ensure changes don't break existing functionality, and test code across multiple browsers and versions. Automated unit tests are more reliable and scalable than manual testing.