This paper presents a mutation analysis tool based on a reflective macro system. Mutation analysis is a powerful and computationally expensive technique that measures the effectiveness of test cases for revealing faults. The principal expense of mutation analysis is that many faulty versions of the program under test, called mutants, must be repeatedly executed. This technique has originally been developed in the framework of procedural programs, and should be re-visited to consider some types of faults likely to appear in object-oriented environments. The mutation system detailed in this paper deals with object-oriented concepts introduced in the JAVA programming language, and is able to generate automatically mutant programs according to 20 types of object-oriented faults.