The MSTest plugin can convert TRX format test reports into JUnit XML format so it can be recorded by Hudson.
To enable the MSTest plugin features you need to set up your build to run MSTest.exe first. Example:

"%PROGRAMFILES%\Microsoft Visual Studio 9.0\Common7\IDE\MSTest.exe" /runconfig:MyTestProject\LocalTestRun.testrunconfig /testcontainer:MyTestProject\bin\Release\MyTestProject.dll /resultsfile:TestResults\testResults.trx

and then specify the path to the MSTest TRX file, such as TestResults/testResults.trx.

You can also run multiple test assemblies. The configuration is similar, you just need to add another testcontainer:

"%PROGRAMFILES%\Microsoft Visual Studio 9.0\Common7\IDE\MSTest.exe" /runconfig:MyTestProject\LocalTestRun.testrunconfig /testcontainer:MyTestProject1\bin\Release\MyTestProject1.dll /testcontainer:MyTestProject2\bin\Release\MyTestProject2.dll /resultsfile:TestResults\testResults.trx

MSTest will run all tests from all assemblies and generate the specified TRX file.