What are the popular test automation tools for Silverlight

I need a test automation tool for Silver开发者_如何转开发light. Basically, I need a tool that would simulate users accessing, clicking buttons etc. on a Silverlight UI.

A google search has turned up several promising leads:

1. WebAii
2. White
3. Selenium-Silverlight
4. NeoLoad

I need to know what the pros and cons of each of them are, and of any other suitable tools for this purpose.

I would prefer a open source tool but am not averse to a proprietary one if necessary.

There's one available in SL4 for unit testing It's quite handy if you do MVVM to write unit tests against your models