The capability of Quantum Computing (QC) in solving complex problems has been increasingly recognized. However, similar to classical computing, to fully exploit QC's potential, it is important to ensure the correctness of quantum programs. Doing so via software testing is, however, very challenging because of QC's inherent properties: superposition and entanglement. Towards the direction of ensuring the correctness of quantum programs, we propose an approach called QuCAT (QUantum CombinAtorial Testing) for systematic and automated testing of quantum programs by benefiting from combinatorial testing, which has been proven to be cost-effective in testing classical programs. QuCAT supports two combinatorial test suite generation scenarios, i.e., generating combinatorial test suites of a given strength, and incrementally generating and executing combinatorial test suites of increasing strength until a fault is found. The approach employs two types of test oracles to assess test results. We performed an empirical study with 18 faulty versions of quantum programs to evaluate QuCAT with strengths of two, three, and four in the two test generation scenarios. We compare the cost-effectiveness of combinatorial testing of various strengths and random testing (taken as baseline approach). Results show that combinatorial testing always performs better than random testing with the same cost and finds faults more quickly (in terms of required number of test cases). In addition, in most cases, combinatorial testing with a higher strength outperforms the lower strength in terms of effectiveness.
The capability of Quantum Computing (QC) in solving complex problems has been increasingly recognized. However, similar to classical computing, to fully exploit QC's potential, it is important to ensure the correctness of quantum programs. Doing so via software testing is, however, very challenging because of QC's inherent properties: superposition and entanglement. Towards the direction of ensuring the correctness of quantum programs, we propose an approach called QuCAT (QUantum CombinAtorial Testing) for systematic and automated testing of quantum programs by benefiting from combinatorial testing, which has been proven to be cost-effective in testing classical programs. QuCAT supports two combinatorial test suite generation scenarios, i.e., generating combinatorial test suites of a given strength, and incrementally generating and executing combinatorial test suites of increasing strength until a fault is found. The approach employs two types of test oracles to assess test results. We performed an empirical study with 18 faulty versions of quantum programs to evaluate QuCAT with strengths of two, three, and four in the two test generation scenarios. We compare the cost-effectiveness of combinatorial testing of various strengths and random testing (taken as baseline approach). Results show that combinatorial testing always performs better than random testing with the same cost and finds faults more quickly (in terms of required number of test cases). In addition, in most cases, combinatorial testing with a higher strength outperforms the lower strength in terms of effectiveness.
With the increased developments in quantum computing, the availability of systematic and automatic testing approaches for quantum programs is becoming increasingly essential. To this end, we present the quantum software testing tool QuCAT for combinatorial testing of quantum programs. QuCAT provides two functionalities of use. With the first functionality, the tool generates a test suite of a given strength (e.g., pairwise). With the second functionality, it generates test suites with increasing strength until a failure is triggered or a maximum strength is reached. QuCAT uses two test oracles to check the correctness of test outputs. We assess the cost and effectiveness of QuCAT with 3 faulty versions of 5 quantum programs. Results show that combinatorial test suites with a low strength can find faults with limited cost, while a higher strength performs better to trigger some difficult faults with relatively higher cost.
The recent fast development of quantum computers breaks several computation limitations that are difficult for conventional computers. Up to the present, although many approaches and tools have been proposed to test quantum programs, the fundamental features of quantum programs, i.e., magnitude, phase, and entanglement, have been largely overlooked, leading to limited fault detection capability and reduced testing effectiveness. To address this problem, we propose an automated testing framework named QURATEST, equipped with three test case generators (including two newly proposed techniques, UCNOT and IQFT in this paper, as well as one based on Random techniques) to test quantum programs. Overall, the proposed generators enable the generation of diverse test inputs by considering the quantum features of quantum programs. In the experiments, we perform an in-depth evaluation of QURATEST from three aspects: generated test case diversity, output coverage of the program under test, and fault detection capability. The results demonstrate the potential of our newly proposed techniques in that IQFT can generate the most diverse test cases regarding magnitude, phase, and entanglement, with 66% cell coverage. Comparatively, the Random approach only has 10% cell coverage. Regarding the evaluations of the output coverage, IQFT can achieve the highest output coverage in 70.2% (33 out of 47) of all quantum programs. In terms of fault detection, UCNOT outperforms the other two techniques. Specifically, the test cases generated by UCNOT have the best mutation score in 88.4% (23 out of 26) quantum programs.
Quantum computing has emerged as an innovative computational paradigm with great potential in various domains. As quantum computing advances, the development of high-quality quantum programs has become crucial, making it essential to ensure their reliability. Software testing plays a vital role in achieving the reliability and quality of software systems. Various testing strategies and tools have been proposed for traditional programs; however, research on testing methodologies for quantum programs is still in the early stages. Traditional testing techniques, while effective for classical programs, struggle to address the unique challenges posed by quantum programs, including inherent characteristics of quantum systems (such as superposition and entanglement), and the exponentially expanding input space as the number of qubits increases. Moreover, traditional testing strategies typically do not account for the hidden and non-deterministic failure patterns associated with input quantum bits (qubits), which, if recognized, could potentially lead to more efficient fault detection. Therefore, in this paper, we introduce a novel approach—Quantum Dynamic-Testing with Incremental Learning (QDT-IL), which aims to effectively capture and adapt to the failure patterns in quantum programs. QDT-IL employs an incremental learning model to learn from executed test cases and continuously updates its predictions on the failure tendencies for new test cases. By utilizing distance-based diversity metrics, QDT-IL strategically increases the variety of test cases, enabling targeted exploration of failure-prone regions in the input space. This combination of adaptive learning and diverse test case selection noticeably enhances the effectiveness and efficiency of quantum program testing. Experimental studies show that QDT-IL outperforms the baseline strategies, providing a more effective testing process for quantum programs.
The inherent complexity of quantum programs, due to features such as superposition and entanglement, makes their testing particularly challenging. To tackle these challenges, we present a search-based approach, called Quantum Search-Based Testing (QuSBT), for automatically generating test suites of a given size that possibly expose failures of the quantum program under test. QuSBT encodes a test suite as a search individual, and tries to maximize the objective function that counts the number of failing tests in the test suite. Due to non-deterministic nature of quantum programs, the approach repeats the execution of each test multiple times, and uses suitable statistical tests to assess if a test passes or fails. QuSBT employs a genetic algorithm to perform the search. Experiments on 30 faulty quantum programs show that QuSBT is statistically better than random search, and is able to efficiently generate maximal failing test suites.
Quantum programs implement quantum algorithms solving complex computational problems. Testing such programs is challenging due to the inherent characteristics of Quantum Computing (QC), such as the probabilistic nature and computations in superposition. However, automated and systematic testing is needed to ensure the correct behavior of quantum programs. To this end, we present an approach called Quito (QUantum InpuT Output coverage) consisting of three coverage criteria defined on the inputs and outputs of a quantum program, together with their test generation strategies. Moreover, we define two types of test oracles, together with a procedure to determine the passing and failing of test suites with statistical analyses. To evaluate the cost-effectiveness of the three coverage criteria, we conducted experiments with five quantum programs. We used mutation analysis to determine the coverage criteria' effectiveness and cost in terms of the number of test cases. Based on the results of mutation analysis, we also identified equivalent mutants for quantum programs.
Generating a test suite for a quantum program such that it has the maximum number of failing tests is an optimization problem. For such optimization, search-based testing has shown promising results in the context of classical programs. To this end, we present a test generation tool for quantum programs based on a genetic algorithm, called QuSBT (Search-based Testing of Quantum Programs). QuSBT automates the testing of quantum programs, with the aim of finding a test suite having the maximum number of failing test cases. QuSBT utilizes IBM’s Qiskit as the simulation framework for quantum programs. We present the tool architecture in addition to the implemented methodology (i.e., the encoding of the search individual, the definition of the fitness function expressing the search problem, and the test assessment w.r.t. two types of failures). Finally, we report results of the experiments in which we tested a set of faulty quantum programs with QuSBT to assess its effectiveness. Repository (code and experimental results): https://github.com/Simula-COMPLEX/qusbt-tool Video: https://youtu.be/3apRCtluAn4