Mutation Testing is an important technique for evaluating the quality of a test suite. Thetechnique involves inserting small changes to the source code of a program to producea set of altered programs, each of which is called a “mutant”. The test suite in questionis considered incomplete when it could not detect the changes made in those mutants.As a result, the findings from mutation testing may lead to a better, improved test suite.The fundamental idea of mutation testing is to imitate the malfunction that may occur inthe program, such as using incorrect mathematical operators, incorrect variable namesand incorrect reference types of the object.This research studies eight mutation operators for OCL (Object Constraint Language).These operators are used to create mutants from OCL specifications in the subset of theUML (Unified Modeling Language) standard. These operators are exmined in twoaspects: (1) the assessment of test coverage of the test suite according to the mutationoperators and (2) the performance of the eight mutation operators when applied in a realworld specficiation. Results from the case study used here indicates that the operatorscan produce mutants effectively where 67% of which are meaningful.