Microsoft Research released their first extension for Visual Studio 2012: Code Digger.
Code Digger analyzes possible execution paths through your .NET code. The result is a table where each row shows a unique behavior of your code. The table helps you understand the behavior of the code, and it may also uncover hidden bugs.
Through the new context menu item "Generate Inputs / Outputs Table" in the Visual Studio editor, you can invoke Code Digger to analyze your code. Code Digger computes and displays input-output pairs. Code Digger systematically hunts for bugs, exceptions, and assertion failures.
You can also try the functionality online through Pex4Fun.
Remark: At the moment Code Digger only works on public .NET code that resides in Portable Class Libraries. This limits its usefulness at the moment.