It's not important because you can do this using MS Build by using command line of MSTest.exe and just pass the dll of the test
<Target Name="UnitTests" AfterTargets="DeployDatabase" Condition="'$(Configuration)' == 'DebugForCheck-in'">
<Message Importance="high" Text="-------------------------------- Running Unit Tests for category 1 only--------------------------------" />
<Message Importance="high" Text=" "/>
<Exec Command='"C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\mstest.exe" /testcontainer:"..\BLTest\bin\Debug\BLTest.dll" /category:cat1' />
</Target>
You can see my post here
http://mohamedradwan.wordpress.com/2010/11/13/automate-the-best-practice-for-check-in-including-get-latest-deploy-db-run-test-check-in/