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 MSTest TRX files, such as TestResults/testResults.trx.