Testing is one method to increase the quality of today's extraordinary complex software.
The aim is to find program errors with respect to given criteria of correctness. In this context, the difficulty of testing object-oriented software arises from the fact that the behavior of an object does not only depend on the input values of the parameters of its operations, but also on its current state, and generally on the current states of other related objects. This combinatorial explosion requires carefully selecting pertinent test sets of reasonable size. This thesis proposes a formal testing method which takes this issue into account.