METRIC+: A metamorphic relation identification technique based on input plus output domains

Metamorphic testing is well known for its ability to alleviate the oracle problem in software testing. The main idea of metamorphic testing is to test a software system by checking whether each identified metamorphic relation (MR) holds among several executions. In this regard, identifying MRs is an essential task in metamorphic testing. In view of the importance of this identification task, METRIC (METamorphic Relation Identification based on Category-choice framework) was developed to help software testers identify MRs from a given set of complete test frames. However, during MR identification, METRIC primarily focuses on the input domain without sufficient attention given to the output domain, thereby hindering the effectiveness of METRIC. Inspired by this problem, we have extended METRIC into METRIC+ by incorporating the information derived from the output domain for MR identification. A tool implementing METRIC+ has also been developed. Two rounds of experiments, involving four real-life specifications, have been conducted to evaluate the effectiveness and efficiency of METRIC+. The results have confirmed that METRIC+ is highly effective and efficient in MR identification. Additional experiments have been performed to compare the fault detection capability of the MRs generated by METRIC+ and those by mMT (another MR identification technique). The comparison results have confirmed that the MRs generated by METRIC+ are highly effective in fault detection.