"FsCheck is a tool for testing .NET programs automatically. You provide a specification of the program, in the form of properties which functions, methods or objects should satisfy, and FsCheck then tests that the properties hold in a large number of randomly generated cases. Such properties are actually a testable specification of your program.Properties are written in F#, C# or VB. FsCheck helps you to define properties, observe the distribution of test data, and define test data generators. Crucially, when a property fails, FsCheck automatically displays a minimal counter example."