The custom ASP.NET NUnit test runner is a simple utility to allow running your NUnit tests inside your ASP.NET application. This is used to allow testing inside an HttpContext without the hassles and pitfalls of trying to fake the context for a test.
I use this test runner on my Sitecore projects to allow unit testing inside the Sitecore application.
loadUI is a free and open source cross-platform Load Testing solution. With a visual, drag-and-drop interface, it allows you to create, configure and redistribute your Load Tests interactively and in real-time.
The Closure Library is a broad, well-tested, modular, and cross-browser JavaScript library. You can pull just what you need from a large set of reusable UI widgets and controls, and from lower-level utilities for DOM manipulation, server communication, animation, data structures, unit testing, rich-text editing, and more.
Web Performance Load Tester is a powerful and easy to use tool that will allow you to automate load testing and generate reports to help you analyze the performance of a web site.
The 10 virtual user version, which is full featured, is free to use and is ideal for identifying pages that exceed a threshold value for further investigation.