Can you recommend reputable companies that offer help (consulting services, etc) in load testing (ASP.NET) web applications? We have a client looking to load test an ASP.NET application and we don't have any expertise in load testing web applications. The client is located in central Massachusetts. My employer http://www.goADNET.com was looking for an option besides, “I can figure out how to do it”.
Do not outsource your testing.
Load testing is best done locally on the actual servers before you go live. This requires root access within the security envelope. Your local network will be capable of generating many more requests on your LAN than could ever come through the internet.
The right choice of tool depends on your total environment, but as soon as you hit a performance issue you'll need intimate knowledge of the code to diagnose it anyhow, which a third-party won't be able to do.
Also, in most apps, true stress testing needs to across your whole architecture, so you'll need to do things like fill up your database with far more records than you'll ever expect to have (by a few orders of magnitude) to test indexes, caching, etc. on the back-end, too.