Equivalent Mutant Problem and its Problem-Solving Techniques: A Retrospective View

Mutation testing is a fault simulating testing technique mainly used to assess the quality of the test suite. During the execution of mutants, some of the mutants remain undetected are known to be equivalent. They also make the mutation testing process costly and time-consuming. Due to the similar behavior of the original program and equivalent mutants, they are unable to be identified by any of the test suites. Researchers have been working in the field to identify and detect equivalent mutants manually and automatically. In this paper, a comprehensive study is done to analyze the problem of equivalent mutants. During the course of this review, several well-known databases were searched for the studies discussing the equivalent mutant problem. A total of 36 studies were found to be relevant to the topic and were evaluated. It is concluded that handling equivalent mutants is the most critical problem; it negatively impacts the test adequacy score. The research work can be categorized into three categories: equivalent mutant detection, how to avoid the generation of equivalent mutants and analyzing the impact of equivalent mutants on different parameters of testing. Compiler optimization techniques and higher order mutation techniques are found to be the most prevailing to distinguish the equivalent mutants from a pool of mutants.