In VS 2013 there seems to be no option to select MSTest instead of VsTest in the Test Runner Dropdown which is also grayed out. Is there a way I can add Mstest to this list as was the case in Vs 2010.
The ability to select MsTest in the Build Definitions of Team Build 2013 is no longer available in the default build process templates. You can still create a custom build process template that runs the old runner, but be aware that the old MsTest runner is in fact considered deprecated.
The dropdown is disabled and there is no way to enable it in the out-of-the-box build process templates.