If you put your BVTs in .vsmdi file in VSTS 2010 and upgrade it to VSTS
2013, we know that .vsmdi is depreciated in VSTS 2012 and VSTS 2013. If you
still like to use .vsmdi file to run your tests in TFS 2013 build, you can still do
it easily.
In TFS 2013 build definition, just choose MSTest Test Meta File (VS 2010 compatible) and do
the configuration as you did in TFS 2010 Build.