Mitigating the effect of coincidental correctness in spectrum based fault localization

2013 Summer.Includes bibliographical references.Coincidentally correct test cases are those that execute faulty program statements but do not result in failures. The presence of such test cases in a test suite reduces the effectiveness of spectrum-based fault localization approaches, such as Ochiai and Tarantula, which localize faulty statements by calculating a suspiciousness score for every program statement from test coverage information. The goal of this dissertation is to improve the understanding of how the presence of coincidentally correct test cases impacts the effectiveness of spectrum-based fault localization approaches and to develop a family of approaches that improve fault localization effectiveness by mitigating the effect of coincidentally correct test cases. Each approach (1)~classifies coincidentally correct test cases using test coverage information, and (2)~recalculates a suspiciousness score for every program statement using the classification information. We developed classification approaches using test coverage metrics at different levels of granularity, such as statement, branch, and function. We developed a new approach for ranking program statements using suspiciousness scores calculated based on the heuristic that the statements covered by more failing and coincidentally correct test cases are more suspicious. We extended the family of fault localization approaches to support multiple faults. We developed an approach to incorporate tester feedback to mitigate the effect of coincidental correctness. The approach analyzes tester feedback to determine a lower bound for the number of coincidentally correct test cases present in a test suite. The lower bound is also used to determine when classification of coincidentally correct test cases can improve fault localization effectiveness. We evaluated the fault localization effectiveness of our approaches and studied how the effectiveness changes for varying characteristics of test suites, such as size, test suite type (e.g., random, coverage adequate), and the percentage of passing test cases that are coincidentally correct. Our key findings are summarized as follows. Mitigating the effect of coincidentally correct test cases improved fault localization effectiveness. The extent of the improvement increased with an increase in the percentage of passing test cases that were coincidentally correct, although no improvement was observed when most passing test cases in a test suite were coincidentally correct. When random test suites were used to localize faults, a coarse-grained coverage spectrum, such as function coverage, resulted in better classification than fine-grained coverage spectra, such as statement and branch coverage. Utilizing tester feedback improved the precision of classification. Mitigating the effect of coincidental correctness in the presence of two faults improved the effectiveness for both faults simultaneously for most faulty programs. Faulty statements that were harder to reach and that affected fewer program statements resulted in fewer coincidentally correct test cases and were more effectively localized

Experimental and theoretical research on program mutation

Issued as Final report, Project no. G-36-636 (continued by G-36-661

Diversifying focused testing for unit testing

Software changes constantly because developers add new features or modifications. This directly affects the effectiveness of the testsuite associated with that software, especially when these new modifications are in a specific area that no test case covers. This paper tackles the problem of generating a high quality test suite to cover repeatedly a given point in a program, with the ultimate goal of exposing faults possibly affecting the given program point. Both search based software testing and constraint solving offer ready, but low quality, solutions to this: ideally a maximally diverse covering test set is required whereas search and constraint solving tend to generate test sets with biased distributions. Our approach, Diversified Focused Testing (DFT), uses a search strategy inspired by GödelTest. We artificially inject parameters into the code branching conditions and use a bi-objective search algorithm to find diverse inputs by perturbing the injected parameters, while keeping the path conditions still satisfiable. Our results demonstrate that our technique, DFT, is able to cover a desired point in the code at least 90% of the time. Moreover, adding diversity improves the bug detection and the mutation killing abilities of the test suites. We show that DFT achieves better results than focused testing, symbolic execution and random testing by achieving from 3% to 70% improvement in mutation score and up to 100% improvement in fault detection across 105 software subjects

The interlocutory tool box: techniques for curtailing coincidental correctness

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonEliminating faults in software systems is important, because they can have catastrophic consequences. This can be achieved by testing and debugging. Testing involves executing the system with a test case to obtain an output. The output is evaluated against the tester’s expectations; deviation from these expectations indicates that a fault has been detected. Debugging involves using information about the fault, that was gleaned during testing, to isolate the fault in the system. Coincidental correctness is a widespread phenomenon in which a fault corrupts a program state, and despite this, the system produces an output that satisfies the tester’s expectations. Coincidental correctness can compromise the effectiveness of testing and debugging techniques. This thesis investigated methods for alleviating coincidental correctness in testing and debugging. The investigation culminated in four techniques. The first technique is called Interlocutory Testing. Interlocutory Testing is a framework for the development of test oracles that are referred to as Interlocutory Relations. Interlocutory Relations are the first type of oracle that has been specifically designed to operate effectively in the presence of coincidental correctness. Metamorphic Testing was pioneered for testing non-testable systems. However, the effectiveness of this technique can be compromised by coincidental correctness. The second technique, Interlocutory Metamorphic Testing, is a version of Metamorphic Testing that has been integrated with Interlocutory Testing, to alleviate the impact of coincidental correctness on Metamorphic Testing. Interlocutory Mutation Testing is the third technique. This technique uses similar principles to Interlocutory Testing to alleviate the Equivalent Mutant Problem in the presence of coincidental correctness and non-determinism. Finally, the fourth technique is Interlocutory Spectrum-based Fault Localisation. This technique uses Interlocutory Relations to ameliorate the effects of coincidental correctness on fault localisation. Each technique was empirically evaluated. The results were promising, and indicated that these techniques were capable of mitigating the impact of coincidental correctness