If you run tests as an MSBuild task in Team Foundation Build, you will probably be interested in a post from Buck Hodges on how to do so without needing to create test metadata files and test lists (.vsmdi files). He created a custom task that will appear in a future release of Team Foundation Server Power Toy.
See his post (Buck Hodges : How to run tests in a build without test metadata files and test lists (.vsmdi files)) for the details and download:
Since the beginning, running tests in Team Build (or MSBuild in general) has meant having to use .vsmdi files to specify the tests to run. Tons of people have complained about it, as it's a burden to create and edit the files, as either VSTS for Testers or the full suite is required in the 2005 release, and merging changes to the file is painful when multiple developers are updating the file. While mstest.exe has a /testcontainer option for simply specifying a DLL or load/web test file, the test tools task used with MSBuild does not expose an equivalent property.