While testing a simple JavaScript is relatively straightforward, testing a complex JavaScript such as a library like Jquery really requires the use of a test suite. Of course you don't necessarily need to develop your own test suite because there are already quite a few around.
The following are a few that I found that look like they may or may not be useful for testing your scripts.
- Sahi – a browser independent automated testing tool that uses Java and JavaScript
- Selenium – an automated testing tool that can record only on Firefox and may time out when trying to play back on other browsers, uses Java and Ruby
- Watir – an automated testing tool available as a Ruby gem
- Assertion Unit Framework – unit testing framework based on assertions
- JsUnit – unit testing framework ported from the most popular Java one
- FireUnit – a unit testing framework designed to run in Firebug on Firefox
- Jspec – a JavaScript testing framework
- Qunit – a Jquery test suite
- JsLitmus – a benchmarking and performance tool