download : http://msdn.microsoft.com/en-us/devlabs/ee692301.aspx

Spec Explorer 2010 is a tool that extends Visual Studio for modeling
software behavior, analyzing that behavior by graphical visualization,
model checking, and generating standalone test code from models.
Behavior is modeled in two ways: by writing rules in C# (with dynamic
data-defined state spaces) and by defining model scenarios as action
patterns in a regular-expression style. One of Spec Explorer’s major
features is the ability to compose models written in these two styles.
This technique enables users to slice out test cases from large state
machines to achieve test purposes by defining relevant scenarios, thus
tackling the notorious state-space explosion problem that is so
pervasive in model-based testing. Spec Explorer also supports
combinatorial interaction testing with a rich set of features.

Past,
Present and Future

During the transition from the now historic
Spec Explorer 2004, Spec Explorer moved from Microsoft Research to an
engineering group in the Windows Server organization where it is being
maintained and grown by a full-fledged development team. Spec Explorer
2010 is shipping in the Visual Studio 2010 time frame in pre-release
version 3.2 to gain user feedback. Please remember the final version may
differ from this one and a final commercial version may not be
released.