Abstract-Executing thorough test suites allows programmers to strengthen the confidence on their software systems. However, given some failed test cases, finding the faults' locations can be a difficult task, thereby techniques that make it easier for the programmer to locate the faulty components are much desirable. In this paper we focus on finding faults in object-oriented, more precisely Java, implementations of data types that are described by algebraic specifications. We capitalize on models for the specification under study and JUnit test suites that cover all axioms of the specification, and present a collection of techniques and underlying methodology, that give the programmer, in a transparent way, a means to locate the fault that causes the implementation to violate the specification. We also present a comparative experiment that was carried out to evaluate this approach where very encouraging results were obtained.