Repeat last test in debug mode in Visual Studio 2013
Joshu Weber at Microsoft said the following when the same question was asked on Microsoft Connect:
Andrew,
This is very interesting feedback. We designed the repeat last run command as a shortcut to selecting a subset of all your tests for execution. It currently by design does not take into account debug attachment as part of a run. This is a interesting new feature idea however and >we are going to place it on our backlog.
Thanks for the feedback. Keep it coming. Joshua Weber
In other words it seems like this isn't possible at the moment (without on add-on at least).
It's possible using ReSharper. Look for the ReSharper.ReSharper_UnitTestSessionRepeatPreviousRun
command in the keyboard bindings options. It can repeat the last test run in debug mode.