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Now showing 1 - 10 of 82
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    Automatically learning usage behavior and generating event sequences for black-box testing of reactive systems
    (The ACM Digital Library, 2019-06) Kıraç, Mustafa Furkan; Aktemur, Tankut Barış; Sözer, Hasan; Gebizli, C. Ş.; Computer Science; KIRAÇ, Mustafa Furkan; AKTEMUR, Tankut Bariş; SÖZER, Hasan
    We propose a novel technique based on recurrent artificial neural networks to generate test cases for black-box testing of reactive systems. We combine functional testing inputs that are automatically generated from a model together with manually-applied test cases for robustness testing. We use this combination to train a long short-term memory (LSTM) network. As a result, the network learns an implicit representation of the usage behavior that is liable to failures. We use this network to generate new event sequences as test cases. We applied our approach in the context of an industrial case study for the black-box testing of a digital TV system. LSTM-generated test cases were able to reveal several faults, including critical ones, that were not detected with existing automated or manual testing activities. Our approach is complementary to model-based and exploratory testing, and the combined approach outperforms random testing in terms of both fault coverage and execution time.
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    A longitudinal case study on Nexus transformation: Impact on productivity, quality, and motivation
    (Wiley, 2023-09) Ersoy, E.; Çallı, E.; Erdoğan, B.; Bağrıyanık, S.; Sözer, Hasan; Computer Science; SÖZER, Hasan
    There have been success stories reported regarding the adoption of agile software development methods in the industry. There also exist observations on their limitations. One of these limitations is scalability since agile methods like Scrum were originally designed for small software teams. Scalable agile frameworks were introduced to address this limitation. We conducted an industrial case study on the adoption of such a framework, called Nexus. Our study involves quantitative and qualitative evaluation based on observations within a product development organization over a period of 12 months. Scrum is used for the development of a product during the first 6 months of this period. Nexus is used in the remaining 6 months. Data are collected throughout the whole period for measuring productivity, quality, and team member motivation. Results suggest a significant increase in productivity and product quality after switching to Nexus. Team motivation was slightly improved as well.
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    Summary of an effective formulation of the multi-criteria test suite minimization problem
    (IEEE, 2022) Özener, Okan Örsan; Sözer, Hasan; Industrial Engineering; Computer Science; ÖZENER, Okan Örsan; SÖZER, Hasan
    This is an extended abstract of the article: Okan Orsan Ozener and Hasan Sozer, 'An Effective Formulation of the Multi-Criteria Test Suite Minimization Problem', published in the Journal of Systems and Software, Vol. 168, pp. 110632, 2020. https://doi.org/10.1016/j.jss.2020.110632.
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    Increasing test efficiency by risk-driven model-based testing
    (Elsevier, 2018-10) Gebizli, C. Ş.; Kırkıcı, A.; Sözer, Hasan; Computer Science; SÖZER, Hasan
    We introduce an approach and a tool, RIMA, for adapting test models used for model-based testing to augment information regarding failure risk. We represent test models in the form of Markov chains. These models comprise a set of states and a set of state transitions that are annotated with probability values. These values steer the test case generation process, which aims at covering the most probable paths. RIMA refines these models in 3 steps. First, it updates transition probabilities based on a collected usage profile. Second, it updates the resulting models based on fault likelihood at each state, which is estimated based on static code analysis. Third, it performs updates based on error likelihood at each state, which is estimated with dynamic analysis. The approach is evaluated with two industrial case studies for testing digital TVs and smart phones. Results show that the approach increases test efficiency by revealing more faults in less testing time.
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    Conference ObjectPublicationOpen Access
    Test kâhini olarak görüntü karşılaştırma algoritmalarının değerlendirilmesi
    (CEUR-WS, 2017) Erdil, Ö. F.; Can, İrfan; Sözer, Hasan; Computer Science; Turhan, Ç.; Coşkunçay, A.; Yazıcı, A.; Oğuztüzün, H.; SÖZER, Hasan; Can, İrfan
    Televizyon gibi yoğun yazılım içeren gömülü sistemlerin kara kutu testleri, grafik kullanıcı arayüzleri (GKA) aracılığıyla gerçekleştirilmektedir. Bu testlerin otomasyonu kapsamında bir dizi kullanıcı işlemi dışarıdan tetiklenmektedir. Bu sırada, doğru ve yanlış sistem davranışı arasında ayrım yapan ve böylece testlerin geçip geçmediğine karar veren otomatik bir test kâhinine ihtiyaç duyulmaktadır. Bu amaçla yaygın olarak görüntü karşılaştırma araçları kullanılmaktadır. Bu araçlar, gözlenen GKA ile daha önceden kaydedilmiş bir referans GKA ekran görüntüsünü karşılaştırmaktadır. Bu çalışmada, 9 farklı görüntü karşılaştırma aracı bir endüstriyel vaka çalışması ile değerlendirildi. Bir televizyon sisteminin gerçek test çalışmalarından 1000 çift referans ve anlık GKA görüntüsü toplandı ve bu görüntüler başarılı/başarısız test olarak etiketlendirildi. Ayrıca, toplanan veri kümesi görüntülerde meydana gelen piksel kayması, renk tonu/doygunluk farklılığı ve resim gövdesinde esneme (büyüme, küçülme, genişleme, daralma) gibi çeşitli etkilere göre sınıflandırıldı. Ardından, bu veri kümesi ile karşılaştırılan araçlar, doğruluk ve performans açısından değerlendirildi. Araçların parametre değerlerine ve karşılaştırılan görüntülerin tâbi oldukları etkilere göre farklı sonuçlar verdiği görülmüştür. Hazırlanan veri kümesi için en iyi sonuçları veren araç ve bu aracın parametre değerleri tespit edilmiştir.
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    Incremental analysis of large-scale system logs for anomaly detection
    (IEEE, 2019) Astekin, M.; Özcan, S.; Sözer, Hasan; Computer Science; SÖZER, Hasan
    Anomalies during system execution can be detected by automated analysis of logs generated by the system. However, large scale systems can generate tens of millions of lines of logs within days. Centralized implementations of traditional machine learning algorithms are not scalable for such data. Therefore, we recently introduced a distributed log analysis framework for anomaly detection. In this paper, we introduce an extension of this framework, which can detect anomalies earlier via incremental analysis instead of the existing offline analysis approach. In the extended version, we periodically process the log data that is accumulated so far. We conducted controlled experiments based on a benchmark dataset to evaluate the effectiveness of this approach. We repeated our experiments with various periods that determine the frequency of analysis as well as the size of the data processed each time. Results showed that our online analysis can improve anomaly detection time significantly while keeping the accuracy level same as that is obtained with the offline approach. The only exceptional case, where the accuracy is compromised, rarely occurs when the analysis is triggered before all the log data associated with a particular session of events are collected.
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    Automated classification of static code analysis alerts: a case study
    (IEEE, 2013) Yüksel, Ulaş; Sözer, Hasan; Computer Science; SÖZER, Hasan; Yüksel, Ulaş
    Static code analysis tools automatically generate alerts for potential software faults that can lead to failures. However, developers are usually exposed to a large number of alerts. Moreover, some of these alerts are subject to false positives and there is a lack of resources to inspect all the alerts manually. To address this problem, numerous approaches have been proposed for automatically ranking or classifying the alerts based on their likelihood of reporting a critical fault. One of the promising approaches is the application of machine learning techniques to classify alerts based on a set of artifact characteristics. In this work, we evaluate this approach in the context of an industrial case study to classify the alerts generated for a digital TV software. First, we created a benchmark based on this code base by manually analyzing thousands of alerts. Then, we evaluated 34 machine learning algorithms using 10 different artifact characteristics and identified characteristics that have a significant impact. We obtained promising results with respect to the precision of classification.
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    Runtime verification of component-based embedded software
    (Springer, 2011) Sözer, Hasan; Hofmann, C; Tekinerdoğan, B.; Akşit, M.; Computer Science; SÖZER, Hasan
    To deal with increasing size and complexity, component-based software development has been employed in embedded systems. Due to several faults, components can make wrong assumptions about the working mode of the system and the working modes of the other components. To detect mode inconsistencies at runtime, we propose a “lightweight” error detection mechanism, which can be integrated with component-based embedded systems. We define links among three levels of abstractions: the runtime behavior of components, the working mode specifications of components and the specification of the working modes of the system. This allows us to detect the user observable runtime errors. The effectiveness of the approach is demonstrated by implementing a software monitor integrated into a TV system.
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    Cost minimization for deploying serverless functions
    (ACM, 2021-03) Sedefoğlu, Ö.; Sözer, Hasan; Computer Science; SÖZER, Hasan
    The costs of serverless functions increase proportional to the amount of memory reserved on the deployed server. However, increasing the amount of memory decreases the function execution time, which is also a factor that contributes to cost. We propose an automated approach for optimizing the amount of memory reserved for serverless functions. First, we measure the running time of a given function in various memory settings and derive a regression model. Then, we define an objective function and a set of constraints based on this regression model and the configuration space. Finally, we determine the optimal memory setting for minimizing cost. Our industrial case study shows that significant cost reductions can be achieved by accurate estimations of the impact of memory settings on runtime performance.
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    VISOR: A fast image processing pipeline with scaling and translation invariance for test oracle automation of visual output systems
    (The ACM Digital Library, 2018-02) Kıraç, Mustafa Furkan; Aktemur, Tankut Barış; Sözer, Hasan; Computer Science; KIRAÇ, Mustafa Furkan; AKTEMUR, Tankut Bariş; SÖZER, Hasan
    A test oracle automation approach proposed for systems that produce visual output.Root causes of accuracy issues analyzed for test oracles based on image comparison.Image processing techniques employed to improve the accuracy of test oracles.A fast image processing pipeline developed as an automated test oracle.An industrial case study performed for automated regression testing of Digital TVs. Test oracles differentiate between the correct and incorrect system behavior. Hence, test oracle automation is essential to achieve overall test automation. Otherwise, testers have to manually check the system behavior for all test cases. A common test oracle automation approach for testing systems with visual output is based on exact matching between a snapshot of the observed output and a previously taken reference image. However, images can be subject to scaling and translation variations. These variations lead to a high number of false positives, where an error is reported due to a mismatch between the compared images although an error does not exist. To address this problem, we introduce an automated test oracle, named VISOR, that employs a fast image processing pipeline. This pipeline includes a series of image filters that align the compared images and remove noise to eliminate differences caused by scaling and translation. We evaluated our approach in the context of an industrial case study for regression testing of Digital TVs. Results show that VISOR can avoid 90% of false positive cases after training the system for 4h. Following this one-time training, VISOR can compare thousands of image pairs within seconds on a laptop computer.