One of the great new features included with .NET 4.5 and Visual Studio 2012 is the async/await support for writing more elegant multi-threaded code in C# or Visual Basic. Support for writing tests that make use of the async/await keywords is available for the Microsoft Test Framework as well as most of the other popular xUnit testing frameworks like NUnit. In addition to providing support for async/await baked into the compilers for Visual Studio 2012 and .NET 4.5, Microsoft has also released the Async Targeting pack for Visual Studio 2012 that enables projects targeting .NET 4.0 or Silverlight 5 to use the Async language feature in C# and Visual Basic code.
Using it in your Silverlight 5 code is quite handy – especially when invoking web services from the client. However, the Microsoft Test Framework for Silverlight has not been extended to support running these asynchronous tests. However, in a recent blog post by Morten Nielsen he shows how it is possible to go about adding this support to the Silverlight Test Framework. He provides a customized version of the Silverlight Test Framework, but also urges us to go vote for getting this added directly to the official Silverlight Toolkit.
I know a lot of development shops like ourselves still have quite a substantial amount of Silverlight code to maintain, so please go and vote for the issue to get Microsoft to add support for it in the Silverlight Toolkit.