I'm calling MSTest like this:
<Target Name='UnitTests'>
<CallTarget Targets="BeforeUnitTests" />
<Exec Command='"$(VS90COMNTOOLS)..\IDE\mstest.exe" /testmetadata:$(SourceCodeRootFolder)ASA.File.Processing.vsmdi /testlist:buildtests' />
<CallTarget Targets="AfterUnitTests" />
</Target>
It's running, but whether it succeeds or fails, no errors are written to the MSBuild error file. I'm running MSBuild with these parms:
/fl /flp:v=detailed;logfile=Errors.txt;errorsonly
I have emails set up to email our team if there are errors in the Errors.txt file.