I know that the question is about VS, but I find useful that when targeting multiple frameworks dotnet tests command will run tests for all frameworks in <TargetFrameworks> node:
> dotnet test
...
Test run for [projectPath]\bin\Debug\netcoreapp1.1\XUnitTestProject.dll(.NETCoreApp,Version=v1.1)
...
Test run for [projectPath]\bin\Debug\net461\XUnitTestProject.dll(.NETFramework,Version=v4.6.1)
...
NCrunch can also recognize multiple targets and run tests for every target automatically:
