The detection of specification errors can help reduce the cost and risk of software development because uncorrected defects in specifications will propagate to code; thus, adversely affecting the quality of the end product. Mutation testing is a well established fault-based technique for assessing and improving the quality of test suites. Mutation testing can be applied at different levels of abstraction, e.g., the unit level, the integration level, and the specification level. In this book, a suite of AsmetaL specific mutation operators are proposed, and classified into four categories. The proposed operators are used to assess the adequacy of test suites generated using the ATGT tool, according to various test coverage criteria. It demonstrates the applicability of the proposed approach through AsmetaL case studies.