Several criteria have been proposed over the years for measuring test suite adequacy. Each criterion can be converted into a specic objective function to optimize with search-based techniques in an attempt to generate test suites achieving the highest possible coverage for that criterion. Recent work has tried to optimize for multiple-criteria at once by constructing a single objective function obtained as a weighted sum of the objective functions of the respective criteria. However, this solution suers the problem of sum scalarization, i.e., dierences along the various dimensions being optimized get lost when such dimensions are projected into a single value. Recent advances in SBST formulated coverage as a many-objective optimization problem rather than applying sum scalarization. Starting from this formulation, in this work, we apply many-objective test generation that handles multiple adequacy criteria simultaneously. To scale the approach to the big number of objectives to be optimized at the same time, we adopt an incremental strategy, where only coverage targets in the control dependency frontier are considered until the frontier is expanded by covering a previously uncovered target.@en

The test case generation is intrinsically a multi-objective problem, since the goal is covering multiple test targets (e.g., branches). Existing search-based approaches either consider one target at a time or aggregate all targets into a single fitness function (whole-suite approach). Multi and many-objective optimisation algorithms (MOAs) have never been applied to this problem, because existing algorithms do not scale to the number of coverage objectives that are typically found in real-world software. In addition, the final goal for MOAs is to find alternative trade-off solutions in the objective space, while in test generation the interesting solutions are only those test cases covering one or more uncovered targets. In this paper, we present Dynamic Many-Objective Sorting Algorithm (DynaMOSA), a novel many-objective solver specifically designed to address the test case generation problem in the context of coverage testing. DynaMOSA extends our previous many-objective technique Many-Objective Sorting Algorithm (MOSA) with dynamic selection of the coverage targets based on the control dependency hierarchy. Such extension makes the approach more effective and efficient in case of limited search budget. We carried out an empirical study on 346 Java classes using three coverage criteria (i.e., statement, branch, and strong mutation coverage) to assess the performance of DynaMOSA with respect to the whole-suite approach (WS), its archive-based variant (WSA) and MOSA. The results show that DynaMOSA outperforms WSA in 28 percent of the classes for branch coverage (+8 percent more coverage on average) and in 27 percent of the classes for mutation coverage (+11 percent more killed mutants on average). It outperforms WS in 51 percent of the classes for statement coverage, leading to +11 percent more coverage on average. Moreover, DynaMOSA outperforms its predecessor MOSA for all the three coverage criteria in 19 percent of the classes with +8 percent more code coverage on average.@en

Context: Replication studies and experiments form an important foundation in advancing scientific research. While their prevalence in Software Engineering is increasing, there is still more to be done. Objective: This article aims to extend our previous replication study on search-based test generation techniques by performing a large-scale empirical comparison with further techniques from state of the art. Method: We designed a comprehensive experimental study involving six techniques, a benchmark composed of 180 non-trivial Java classes, and a total of 21,600 independent executions. Metrics regarding effectiveness and efficiency of the techniques were collected and analyzed by means of statistical methods. Results: Our empirical study shows that single target approaches are generally outperformed by multi-target approaches, while within the multi-target approaches, DynaMOSA/ MOSA, which are based on many-objective optimization, outperform the others, in particular for complex classes. Conclusion: The results obtained from our large-scale empirical investigation confirm what has been reported in previous studies, while also highlighting striking differences and novel observations. Future studies, on different benchmarks and considering additional techniques, could further reinforce and extend our findings.@en

Replication is a fundamental pillar in the construction of scientific knowledge. Test data generation for procedural programs can be tackled using a single-target or a many-objective approach. The proponents of LIPS, a novel single-target test generator, conducted a preliminary empirical study to compare their approach with MOSA, an alternative many-objective test generator. However, their empirical investigation suffers from several external and internal validity threats, does not consider complex programs with many branches and does not include any qualitative analysis to interpret the results. In this paper, we report the results of a replication of the original study designed to address its major limitations and threats to validity. The new findings draw a completely different picture on the pros and cons of single-target vs many-objective approaches to test case generation.

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EvoSuite-MOSA is a unit test data generation tool that employs a novel many-objective optimization algorithm suitably developed for branch coverage. It was implemented by extending the Evo Suite test data generation tool. In this paper we present the results achieved by EvoSuite-MOSA in the third Unit Testing Tool Competition at SBST'15. Among six participants, EvoSuite-MOSA stood third with an overall score of 189.22.@en

Test data generation has been extensively investigated as a search problem, where the search goal is to maximize the number of covered program elements (e.g., branches). Recently, the whole suite approach, which combines the fitness functions of single branches into an aggregate, test suite-level fitness, has been demonstrated to be superior to the traditional single-branch at a time approach. In this paper, we propose to consider branch coverage directly as a many-objective optimization problem, instead of aggregating multiple objectives into a single value, as in the whole suite approach. Since programs may have hundreds of branches (objectives), traditional many-objective algorithms that are designed for numerical optimization problems with less than 15 objectives are not applicable. Hence, we introduce a novel highly scalable many-objective genetic algorithm, called MOSA (Many-Objective Sorting Algorithm), suitably defined for the many-objective branch coverage problem. Results achieved on 64 Java classes indicate that the proposed many-objective algorithm is significantly more effective and more efficient than the whole suite approach. In particular, effectiveness (coverage) was significantly improved in 66% of the subjects and efficiency (search budget consumed) was improved in 62% of the subjects on which effectiveness remains the same.@en