Abstract. Lurette is an automated testing tool dedicated to reactive programs. The test process is automated at two levels: given a formal description of the System Under Test (SUT) environment, Lurette generates realistic input sequences; and, given a formal description of expected properties, Lurette performs the test results analysis. Lurette has been re-implemented from scratch. In this new version, the main novelty lies in the way the SUT environment is described. This is done by means of a new language called Lucky, dedicated to the programming of probabilistic reactive systems. This article recalls the principles of Lurette, briefly presents the Lucky language, and describes some cases studies from the IST project Safeair II. The objective is to illustrate the usefulness of Lurette on real case studies, and the expressiveness of Lucky in accurately describing SUT environments. We show in particular how Lurette can be used to test a typical fault-tolerant system; we also present...