From the research web site:
The Spec# programming system is a new attempt at a more cost effective way to develop and maintain high-quality software. The system consists of:
- A programming methodology, which includes a sound treatment of object invariants in object-oriented programs.
- The Spec# programming language, which is a superset of C# and adds things like non-null types, checked exceptions, method contracts (like pre- and postconditions), and object invariants.
- The Spec# compiler, which is integrated into the Microsoft Visual Studio development environment, statically enforces non-null types, emits run-time checks for method contracts and invariants, and records the specifications in metadata for consumption by the program verifier.
- The Spec# static program verifier, which translates programs into logical verification conditions, which are passed to an automatic theorem prover.
- An interface to the SpecExplorer tool for test generation and model-based testing.
More info: http://research.microsoft.com/SpecSharp/