- Regression testing is a common and necessary task carried out by software practitioners to validate the quality of evolving software systems. Unfortunately, regression testing is often an expensive, time-consuming process, particularly when applied to large software systems. Consequently, practitioners may wish to prioritize the test cases in their regression test suites to execute more importation test cases earlier in the regression testing process. One common goal of this test case prioritization is to increase a test suite’s rate of fault detection, a measure of how quickly faults are detected by a test suite. Recent research has begun to incorporate the practical issues of varying test costs, tests criticalities and fault severities into test case prioritization techniques and metrics measuring the rate of fault detection of these techniques. However, more empirical data is needed to sufficiently examine both the metrics and techniques developed by this research. To address this need, we conducted a case study to further examine the effectiveness of various prioritization techniques that incorporate varying test costs and criticalities. Software practitioners can use the results of this study to help enhance the effectiveness of their regression testing procedures and, in doing so, improve the quality of their software.