This extension added (contains) tool for testing regular expressions in Visual Studio 2010, 2012 and 2013.
Tool simple and easy to use, the processing occurs in a background thread.
http://visualstudiogallery.msdn.microsoft.com/16b9d664-d88c-460e-84a5-700ab40ba452
Third party stuff includes: Slightly modified version of CodeBox-2 * Added support for decorating a zero width text range and end-of-line with background color. Such a decoration shows as narrow vertical bar between two characters just before and just after the range. * Converted project to Visual Studio 2013 format
http://www.codeproject.com/Articles/35413/CodeBox-2-An-Extended-and-Improved-Version-of-the
seealso: http://www.codeproject.com/Articles/33939/CodeBox
and: http://devhawk.net/2009/07/09/syntax-highlighting-textboxes-in-wpf-a-sad-story/