QUnit: Testing JavaScript

For getting started with QUnit, a testing framework for JavaScript, see a good introductory article here. This text is part of QUnit documentation. See Intro to Unit Testing (link).
Below are additional useful resources.

• QUnit Presentation (link)
• Cookbook (link)
• API Documentation (link)
• Article in MSDN Magazine (link)

Besides QUnit, there is Sinon.JS (link), a mock/stub framework. Useful when mocking window functions, for example.