Support for testing all possible sequences of method invocations for a single object is describe in [XXX]. The approach relies, however, on an algebraic specification of the properties of the object and seems to be suitable primarily for testing associativity and commutativity properties of methods. For example, it may be important to know that a method has no influence on the state of the object. Algebraically, this may be expressed by allowing the emthod to commute with every other method call, since the method behaves as the identity on the state of the object. Also in a more general (that is state-based) approach this property may be of importance. See section X-corr. Actually, the C++ specifier const provides a facility to inform the compiler of this property.