This morning, the VSTS Rangers released to Codeplex a new beta of the WCF Load Test tool adding support for ASMX web services. Download it from here.
This tool takes a WCF trace file and a WCF client proxy, or a WCF interface contract, and generates a unit test that replays the same sequence of calls found in the trace file. The code generated is easily modifiable so that data variation can be introduced for the purpose of doing performance testing.The tool generates code for both Visual Studio 2005 and Visual Studio 2008. It also installs a wizard into both editions of Visual Studio for creating the trace and processing it from inside Visual Studio. If both editions are present the tool is installed into both editions. The source code is a Visual Studio 2005 project.