In [L. Feijs, et al., 2000] we proposed a generalization of the TorX test derivation algorithm with probabilities. The current work extends the theoretical work from [L. Feijs, et al., 2000], by presenting experimental results obtained with the probabilistic TorX. The experiment with the distributed conference protocol case study confirms that the extension of the algorithm with explicit probabilities leads to improvements in the tests generated with respect to the chances of finding errors in the implementation