Test Oracles Research Articles

Sasa: a SimulAtor of Self-stabilizing Algorithms

Abstract In this paper, we present sasa, an open-source SimulAtor of Self-stabilizing Algorithms. Self-stabilization defines the ability of a distributed algorithm to recover after transient failures. sasa is implemented as a faithful representation of the atomic-state model (also called the locally shared memory model with composite atomicity). This model is the most commonly used one in the self-stabilizing area to prove both the correct operation of self-stabilizing algorithms and complexity bounds on them. sasa encompasses all features necessary to debug, test and analyze self-stabilizing algorithms. All these facilities are programmable to enable users to accommodate to their particular needs. For example, asynchrony is modeled by programmable stochastic daemons playing the role of input sequence generators. Properties of algorithms can be checked using formal test oracles. The sasa distribution also provides several facilities to easily achieve (batch-mode) simulation campaigns. We show that the lightweight design of sasa allows to efficiently perform huge such campaigns. Following a modular approach, we have aimed at relying as much as possible the design of sasa on existing tools, including ocaml, dot and several tools developed in the Synchrone Group of the VERIMAG laboratory.

ПЕРЕВАГИ ТА НЕДОЛІКИ СМАРТ-КОНТРАКТІВ У ЗОБОВ’ЯЗАЛЬНОМУ ПРАВІ

The article analyzes the positive and negative aspects of the use of smart contracts in various business areas, which respectively give it an advantage or disadvantage compared to traditional civil law contracts. It has been determined that due to the automatic execution of the transaction, as soon as the agreed conditions are fulfilled, smart contracts allow eliminating or minimizing a number of transaction costs that accompany traditional contracts. When using a smart contract, the possibility of improper execution by one of the parties is practically eliminated, since it cannot be violated. It is the difficulty of modifying or terminating smart contracts that is an advantage over other contractual structures. The complexity of changing and terminating smart contracts is a guarantee of their stability and the immutability of the contractual terms that were originally agreed by the parties. But at the same time, smart contracts, eliminating some of the problems of traditional contracts, create new ones when using them. The article also notes that smart contracts are distinguished by both vulnerability in computer code and insufficiently effective legal regulation. The problem of oracles when using smart contracts is considered, which consists in the need to trust the information received from them. It is concluded that due to the vulnerability of a smart contract, like any modern digital technology, the existence of a written original of the contract, subsequently expressed in a smart contract, will make it much easier for the parties to use both judicial and extrajudicial methods to protect their rights. It has been noted that due to the growing use of smart contracts in civil circulation, the number of disputes arising in connection with this, considered both in state courts and in non-state bodies (arbitration courts), will also increase.

NeuralD: Detecting Indistinguishability Violations of Oblivious RAM With Neural Distinguishers

Adversaries can deduce confidential information processed by a program by analyzing its memory access patterns. Oblivious RAM (ORAM) converts a sequence of program memory accesses to an oblivious form, hence preventing adversarial inference. In recent years, a flourishing growth of sophisticated and effective ORAM protocols has occurred. Nonetheless, due to the complexity of these protocols, some of them contain defects in their implementations or even in their design, jeopardizing their obliviousness when processing certain memory access sequences. In this paper, we present <monospace>NeuralD</monospace>, a practical tool for testing ORAM protocols and detecting violations of their stated obliviousness. We train a neural distinguisher to form a <i>probabilistic testing oracle</i> capable of determining with a bounded high probability if a pair of ORAM inputs violates the obliviousness guarantee. <monospace>NeuralD</monospace> incorporates a set of techniques and optimizations to provide a highly effective and practical testing pipeline. Additionally, it features a delta debugging-like method to minimize error-triggering inputs (i.e., counterexamples) &#x2014; developers can use these counterexamples to debug their ORAM protocols and identify root problems. <monospace>NeuralD</monospace> is evaluated using well-known ORAM protocols and real-world ORAM applications (e.g., secure key-value storage). Within a few minutes, <monospace>NeuralD</monospace> can detect subtle violations of stated obliviousness.

Identifying Incorrect Patches in Program Repair Based on Meaning of Source Code

Automatic Program Repair (APR) techniques have shown the potential of reducing debugging costs while improving software quality by generating patches for fixing bugs automatically. However, they often generate many overfitting patches which pass only a specific test-suite but do not fix the bugs correctly. This paper proposes MIPI, a novel approach to reducing the number of overfitting patches generated in the APR. We leverage recent advances in deep learning to exploit the similarity between the patched method&#x2019;s name (which often encloses the developer&#x2019;s intention about the code) and the semantic meaning of the method&#x2019;s body (which represents the actual implemented behavior) for identifying and removing overfitting patches generated by APR tools. Experiments with a large dataset of patches for QuixBugs and Defects4J programs show the promise of our approach. Specifically, in a total of 1,191 patches generated by 23 existing APR tools, MIPI successfully filters out 254 (32&#x0025;) of the total 797 overfitting patches with a precision of 90&#x0025; while preserving 93&#x0025; of the correct patches. MIPI is more precise and less damaging to the APR than existing heuristic patch assessment techniques, achieving a higher recall than automated testing-based techniques that do not have access to the test oracle. In addition, MIPI is highly complementary to existing automated patch assessment techniques.

Data-Driven Representations for Testing Independence: Modeling, Analysis and Connection With Mutual Information Estimation

This work addresses testing the independence of two continuous and finite-dimensional random variables from the design of a data-driven partition. The empirical log-likelihood statistic is adopted to approximate the sufficient statistics of an oracle test against independence (that knows the two hypotheses). It is shown that approximating the sufficient statistics of the oracle test offers a learning criterion for designing a data-driven partition that connects with the problem of mutual information estimation. Applying these ideas in the context of a data-dependent tree-structured partition (TSP), we derive conditions on the TSP's parameters to achieve a strongly consistent distribution-free test of independence over the family of probabilities equipped with a density. Complementing this result, we present finite-length results that show our TSP scheme's capacity to detect the scenario of independence structurally with the data-driven partition as well as new sampling complexity bounds for this detection. Finally, some experimental analyses provide evidence regarding our scheme's advantage for testing independence compared with some strategies that do not use data-driven representations.

Combinatorial methods for testing Internet of Things smart home systems

SummaryIn this paper, we report on applying combinatorial testing to Internet of Things (IoT) home automation hub systems. We detail how to create a dedicated input parameter model of an IoT home automation hub system for use with combinatorial test case generation strategies. Further, we developed an automated test execution framework and two test oracles for evaluation purposes. We applied and evaluated our proposed methodological approach to a real‐world IoT system and analysed the obtained results of various combinatorial test sets with different properties generated based on the derived input model. Additionally, we compare these results to a random testing approach. Our empirical testing evaluations revealed multiple errors in the tested devices and also showed that all considered approaches performed nearly equally well.

Syntax‐based metamorphic relation prediction via the bagging framework

AbstractSoftware testing is an indispensable part of the software engineering industry, which guarantees product reliability and safety. Traditional testing approaches face the testing Oracle problem, they are difficult to construct the expected outputs with the increasing of program complexity. As a result, metamorphic testing, which tests the program by examining the relationship between the execution results, is proposed. However, existing manual metamorphic relation construction requires huge effects of domain experts, and automatic methods are unstable and inefficient due to the insufficient software feature mining. Hence, we proposed a multi‐dimensional program structure‐based metamorphic relation prediction approach, which is composed of feature extraction and prediction model building. In the feature extraction stage, the testing program is converted to multiple intermediate structures (such as control flow graphs and abstract syntax trees) to explore its features. In the prediction model building stage, the extracted feature set is used as the training set, and a novel semi‐supervised support vector machine‐bagging‐K‐nearest neighbors algorithm is designed to train the prediction model. Besides, a two‐phase hybrid granularity search algorithm is proposed to improve the prediction performance by selecting the optimal number of weak classifiers. Compared with existing approaches, our proposed model can improve the accuracy by around 14%.

Fully automated functional fuzzing of Android apps for detecting non-crashing logic bugs

Android apps are GUI-based event-driven software and have become ubiquitous in recent years. Obviously, functional correctness is critical for an app’s success. However, in addition to crash bugs, non-crashing functional bugs (in short as “non-crashing bugs” in this work) like inadvertent function failures, silent user data lost and incorrect display information are prevalent, even in popular, well-tested apps. These non-crashing functional bugs are usually caused by program logic errors and manifest themselves on the graphic user interfaces (GUIs). In practice, such bugs pose significant challenges in effectively detecting them because (1) current practices heavily rely on expensive, small-scale manual validation ( the lack of automation ); and (2) modern fully automated testing has been limited to crash bugs ( the lack of test oracles ). This paper fills this gap by introducing independent view fuzzing , a novel, fully automated approach for detecting non-crashing functional bugs in Android apps. Inspired by metamorphic testing, our key insight is to leverage the commonly-held independent view property of Android apps to manufacture property-preserving mutant tests from a set of seed tests that validate certain app properties. The mutated tests help exercise the tested apps under additional, adverse conditions. Any property violations indicate likely functional bugs for further manual confirmation. We have realized our approach as an automated, end-to-end functional fuzzing tool, Genie. Given an app, (1) Genie automatically detects non-crashing bugs without requiring human-provided tests and oracles (thus fully automated ); and (2) the detected non-crashing bugs are diverse (thus general and not limited to specific functional properties ), which set Genie apart from prior work. We have evaluated Genie on 12 real-world Android apps and successfully uncovered 34 previously unknown non-crashing bugs in their latest releases — all have been confirmed, and 22 have already been fixed. Most of the detected bugs are nontrivial and have escaped developer (and user) testing for at least one year and affected many app releases, thus clearly demonstrating Genie’s effectiveness. According to our analysis, Genie achieves a reasonable true positive rate of 40.9%, while these 34 non-crashing bugs could not be detected by prior fully automated GUI testing tools (as our evaluation confirms). Thus, our work complements and enhances existing manual testing and fully automated testing for crash bugs.

Test Oracle Generation Based on BPNN by Using the Values of Variables at Different Breakpoints for Programs

Automatic test oracle generation is a bottleneck in realizing full automation of the entire software testing process. This study proposes a new method for automatically generating a test oracle for a new test input on the basis of several historical test cases by using a backpropagation neural network (BPNN) model. The new method is different from existing test oracle techniques. Specifically, our method has two steps. First, the values of variables are collected as training data when several historical test inputs are used to execute the program at different breakpoints. The test oracles (pass or fail) of these test cases are utilized to classify and label the training data. Second, a new test input is used to execute the program at different breakpoints, where the trained BPNN prediction model automatically generates its test oracle on the basis of the collected values of the variables involved. We conduct an experiment to validate our method. In the experiment, 113 faulty versions of seven types of programs are used as experimental objects. Results show that the average prediction accuracy rate of 74,651 test oracles is 95.8%. Although the failed test cases in the training data account for less than 5%, the overall average recall rate (prediction accuracy of test case execution failure) of all programs is 78.9%. Furthermore, the trained BPNN can reveal not only the impact of the values of variables but also the impact of the logical correspondence between variables in test oracle generation.

Testing Deep Learning-based Visual Perception for Automated Driving

Due to the impressive performance of deep neural networks (DNNs) for visual perception, there is an increased demand for their use in automated systems. However, to use deep neural networks in practice, novel approaches are needed, e.g., for testing. In this work, we focus on the question of how to test deep learning-based visual perception functions for automated driving. Classical approaches for testing are not sufficient: A purely statistical approach based on a dataset split is not enough, as testing needs to address various purposes and not only average case performance. Additionally, a complete specification is elusive due to the complexity of the perception task in the open context of automated driving. In this article, we review and discuss existing work on testing DNNs for visual perception with a special focus on automated driving for test input and test oracle generation as well as test adequacy. We conclude that testing of DNNs in this domain requires several diverse test sets. We show how such tests sets can be constructed based on the presented approaches addressing different purposes based on the presented methods and identify open research questions.

Path-directed source test case generation and prioritization in metamorphic testing

Metamorphic testing is a technique that makes use of some necessary properties of the software under test, termed as metamorphic relations, to construct new test cases, namely follow-up test cases, based on some existing test cases, namely source test cases. Due to the ability of verifying testing results without the need of test oracles, it has been widely used in many application domains and detected lots of real-life faults. Numerous investigations have been conducted to further improve the effectiveness of metamorphic testing, most of which were focused on the identification and selection of “good” metamorphic relations. Recently, a few studies emerged on the research direction of how to generate and select source test cases that are effective in fault detection. In this paper, we propose a novel approach to generating source test cases based on their associated path constraints, which are obtained through symbolic execution. The path distance among test cases is leveraged to guide the prioritization of source test cases, which further improve the efficiency. A tool has been developed to automate the proposed approach as much as possible. Empirical studies have also been conducted to evaluate the fault-detection effectiveness of the approach. The results show that this approach enhances both the performance and automation of metamorphic testing. It also highlights interesting research directions for further improving metamorphic testing.

Using metamorphic relations to verify and enhance Artcode classification

Software testing is often hindered where it is impossible or impractical to determine the correctness of the behaviour or output of the software under test (SUT), a situation known as the oracle problem. An example of an area facing the oracle problem is automatic image classification, using machine learning to classify an input image as one of a set of predefined classes. An approach to software testing that alleviates the oracle problem is metamorphic testing (MT). While traditional software testing examines the correctness of individual test cases, MT instead examines the relations amongst multiple executions of test cases and their outputs. These relations are called metamorphic relations (MRs): if an MR is found to be violated, then a fault must exist in the SUT. This paper examines the problem of classifying images containing visually hidden markers called Artcodes, and applies MT to verify and enhance the trained classifiers. This paper further examines two MRs, Separation and Occlusion, and reports on their capability in verifying the image classification using one-way analysis of variance (ANOVA) in conjunction with three other statistical analysis methods: t-test (for unequal variances), Kruskal–Wallis test, and Dunnett’s test. In addition to our previously-studied classifier, that used Random Forests, we introduce a new classifier that uses a support vector machine, and present its MR-augmented version. Experimental evaluations across a number of performance metrics show that the augmented classifiers can achieve better performance than non-augmented classifiers. This paper also analyses how the enhanced performance is obtained.

The Blockchain Oracle Problem in Decentralized Finance—A Multivocal Approach

Decentralized Finance (DeFi) takes the promise of blockchain a step further and aims to transform traditional financial products into trustless and transparent protocols that run without involving intermediaries. Similar to how 2017 was the year of ICOs, 2020 was the year of DeFi, with more than fifteen billion dollars of total investments. The decentralized platforms utilize oracles to retrieve asset data from the external world, but their choice and management criteria are often unknown to the end-users. If oracles are poorly selected or managed, the funds of a rising number of investors are inevitably in danger. The issue, known as “the oracle problem”, which makes real-world applications controversial and debated due to the loss of decentralization, had recently drawn attention to DeFi, given the crescent number of related hacks that caused the loss of millions of dollars held in DeFi projects. Through a multivocal approach that considers academic papers, whitepapers, preprints, and opinion posts, this study aims to shed light on the pattern that identifies the oracle problem in DeFi and outline the most promising ways to overcome the related weaknesses. This research supports the view that the oracle problem in decentralized finance bears specific characteristics which require standardization and appropriate economic incentives to be addressed.

Testing multiple linear regression systems with metamorphic testing

Regression is one of the most commonly used statistical techniques. However, testing regression systems is a great challenge because of the absence of test oracle in general. In this paper, we show that Metamorphic Testing is an effective approach to test multiple linear regression systems. In doing so, we identify intrinsic mathematical properties of linear regression, and then propose 11 Metamorphic Relations to be used for testing. Their effectiveness is examined using mutation analysis with a range of different regression programs. We further look at how the testing could be adopted in a more effective way. Our work is applicable to examine the reliability of predictive systems based on regression that has been widely used in economics, engineering and science, as well as of the regression calculation manipulated by statistical users.

Embedding and classifying test execution traces using neural networks

Classifying test executions automatically as pass or fail remains a key challenge in software testing and is referred to as the test oracle problem. It is being attempted to solve this problem with supervised learning over test execution traces. A programme is instrumented to gather execution traces as sequences of method invocations. A small fraction of the programme's execution traces is labelled with pass or fail verdicts. Execution traces are then embedded as fixed length vectors and a neural network (NN) component that uses the line-by-line information to classify traces as pass or fail is designed. The classification accuracy of this approach is evaluated using subject programs from different application domains—1. Module from Ethereum Blockchain, 2. Module from PyTorch deep learning framework, 3. Microsoft SEAL encryption library components, 4. Sed stream editor, 5. Nine network protocols from Linux packet identifier, L7-Filter and 6. Utilities library, commons-lang for Java. For all subject programs, it was found that test execution classification had high precision, recall and specificity, averaging to 93%, 94% and 96%, respectively, while only training with an average 14% of the total traces. Experiments show that the proposed NN-based approach is promising in classifying test executions from different application domains.

MeMo: Automatically identifying metamorphic relations in Javadoc comments for test automation

Software testing depends on effective oracles. Implicit oracles, such as checks for program crashes, are widely applicable but narrow in scope. Oracles based on formal specifications can reveal application-specific failures, but specifications are expensive to obtain and maintain. Metamorphic oracles are somewhere in-between. They test equivalence among different procedures to detect semantic failures. Until now, the identification of metamorphic relations has been a manual and expensive process, except for few specific domains where automation is possible. We present MeMo, a technique and a tool to automatically derive metamorphic equivalence relations from natural language documentation, and we use such metamorphic relations as oracles in automatically generated test cases. Our experimental evaluation demonstrates that 1) MeMo can effectively and precisely infer equivalence metamorphic relations, 2) MeMo complements existing state-of-the-art techniques that are based on dynamic program analysis, and 3) metamorphic relations discovered with MeMo effectively detect defects when used as test oracles in automatically-generated or manually-written test cases.

A Machine Learning Based Framework for Verification and Validation of Massive Scale Image Data

Big data validation and system verification are crucial for ensuring the quality of big data applications. However, a rigorous technique for such tasks is yet to emerge. During the past decade, we have developed a big data system called CMA for investigating the classification of biological cells based on cell morphology which is captured in diffraction images. CMA includes a collection of scientific software tools, machine learning algorithms, and a large-scale cell image repository. In order to ensure the quality of big data system CMA, we developed a framework for rigorously validating the massive scale image data as well as adequately verifying both the software tools and machine learning algorithms. The validation of big data is conducted by iteratively selecting the data using a machine learning approach. An experimental approach guided by a feature selection algorithm is introduced in the framework to select an optimal feature set for improving the machine learning performance. The verification of software and algorithms is developed on the iterative metamorphic testing approach due to the non-testable property of the software and algorithms. A machine learning approach is introduced for developing test oracles iteratively to ensure the adequacy of the test coverage criteria. Performance of the machine learning algorithm is evaluated with a stratified N-fold cross validation and confusion matrix. We describe the design of the proposed big data verification and validation framework with CMA as the case study, and demonstrate its effectiveness through verifying and validating the dataset, the software and the algorithms in CMA.

Towards effective metamorphic testing by algorithm stability for linear classification programs

The quality assurance for machine learning systems is becoming increasingly critical nowadays. While many efforts have been paid on trained models from such systems, we focus on the quality of these systems themselves, as the latter essentially decides the quality of numerous models thus trained. In this article, we focus particularly on detecting bugs in implementing one class of model-training systems, namely, linear classification algorithms, which are known to be challenging due to the lack of test oracle. Existing work has attempted to use metamorphic testing to alleviate the oracle problem, but fallen short on overlooking the statistical nature of such learning algorithms, leading to premature metamorphic relations (MRs) suffering efficacy and necessity issues. To address this problem, we first derive MRs from a fundamental property of linear classification algorithms, i.e., algorithm stability, with the soundness guarantee. We then formulate such MRs in a way that is rare in usage but could be more effective according to our field study and analysis, i.e., Past-execution Dependent MR (PD-MR), as contrast to the traditional way, i.e., Past-execution Independent MR (PI-MR), which has been extensively studied. We experimentally evaluated our new MRs upon nine well-known linear classification algorithms. The results reported that the new MRs detected 37.6–329.2% more bugs than existing benchmark MRs.

Preparing Auditors for the Blockchain Oracle Problem

SUMMARYThis article summarizes “Auditing the Blockchain Oracle Problem” (Sheldon 2021), which introduces auditors to the risks of having an irreversible business agreement codified on a blockchain using a short software program called a smart contract that relies on an oracle to provide information from outside the blockchain in order to execute correctly. The article begins with an explanation of the role that oracles play in the blockchain ecosystem and proposes a working definition of oracles. Next, the article highlights how the auditing standards from both the AICPA and PCAOB can be interpreted to classify an oracle as part of smart contract users' information systems, and that the oracle provides a robust set of services that qualify it as a service organization. Finally, the article describes the process used by an oracle to collect, store, transform, and transmit data, and highlights relevant risks and illustrative control objectives related to this process.

Ontology-based metamorphic testing for chatbots

Modern-day demands for services often require an availability on a 24/7 basis as well as online accessibility around the globe. For this sake, personalized virtual assistants, called chatbots, are implemented. Such systems offer services, goods or information in natural language. These natural language processing (NLP) programs respond to the user in real time and offer an intuitive and simple interface to interact with. Advantages like these make them increasingly popular. Therefore, ensuring correct functionality of chatbots is of increasing importance. However, since different implementations and user behaviour result in unpredictable results, the chatbot’s input and output data are difficult to predict and classify as well. Under such circumstances, test cases can be inferred from the domain of possible inputs of a system under test (SUT). Ontologies are concepts used in AI to provide formal representations of knowledge for a specific domain. Such ontological models contain structured information that is used for test generation. On the other hand, testing of chatbots represents a challenge because of the absence of a test oracle. In this paper, both challenges are addressed by conceptualizing ontologies for input generation and output processing in form of a metamorphic testing approach. In this scenario, both concepts are applied for automated testing of chatbots. The approach is demonstrated on a real system from the tourism domain, thereby discussing the obtained results.