Toward granular search-based automatic unit test case generation

Automatic unit test generation that explores the input space and produces effective test cases for given programs have been studied for decades. Many unit test generation tools that can help generate unit test cases with high structural coverage over a program have been examined. However, the fact that existing test generation tools are mainly evaluated on general software programs calls into question about its practical effectiveness and usefulness for machine learning libraries, which are statistically orientated and have fundamentally different nature and construction from general software projects. In this paper, we set out to investigate the effectiveness of existing unit test generation techniques on machine learning libraries. To investigate this issue, we conducted an empirical study on five widely used machine learning libraries with two popular unit testcase generation tools, i.e., EVOSUITE and Randoop. We find that (1) most of the machine learning libraries do not maintain a high-quality unit test suite regarding commonly applied quality metrics such as code coverage (on average is 34.1%) and mutation score (on average is 21.3%), (2) unit test case generation tools, i.e., EVOSUITE and Randoop, lead to clear improvements in code coverage and mutation score, however, the improvement is limited, and (3) there exist common patterns in the uncovered code across the five machine learning libraries that can be used to improve unit test case generation tasks.

Automated test generation has been extensively studied for dynamically compiled or typed programming languages like Java and Python. However, Go, a popular statically compiled and typed programming language for server application development, has received limited support from existing tools. To address this gap, we present NxtUnit, an automatic unit test generation tool for Go that uses random testing and is well-suited for microservice architecture. NxtUnit employs a random approach to generate unit tests quickly, making it ideal for smoke testing and providing quick quality feedback. It comes with three types of interfaces: an integrated development environment (IDE) plugin, a command-line interface (CLI), and a browser-based platform. The plugin and CLI tool allow engineers to write unit tests more efficiently, while the platform provides unit test visualization and asynchronous unit test generation. We evaluated NxtUnit by generating unit tests for 13 open-source repositories and 500 ByteDance in-house repositories, resulting in a code coverage of 20.74% for in-house repositories. We conducted a survey among Bytedance engineers and found that NxtUnit can save them 48% of the time on writing unit tests. We have made the CLI tool available at https://github.com/bytedance/nxt_unit.

Code coverage-guided unit test generation (CGTG) and large language model-based test generation (LLMTG) are two principal approaches for the generation of unit tests. Each of these approaches has its inherent advantages and drawbacks. Tests generated by CGTG have been shown to exhibit high code coverage and high executability. However, they lack the capacity to comprehend code intent, which results in an inability to identify deviations between code implementation and design intent (i.e., functional defects). Conversely, although LLMTG demonstrates an advantage in terms of code intent analysis, it is generally characterized by low executability and necessitates iterative debugging. In order to enhance the ability of unit test generation to identify functional defects, a novel framework has been proposed, entitled the intent analysis-guided unit test generation and refinement (IGTG&R) model. The IGTG&R model consists of a two-stage process for test generation. In the first stage, we introduce coverage path entropy to enhance CGTG to achieve high executability and code coverage of test cases. The second stage refines the test cases using LLMs to identify functional defects. We quantify and verify the interference of incorrect code implementation on intent analysis through conditional entropy. In order to reduce this interference, the focal method body is excluded from the code context information during intent analysis. Using these two-stage process, IGTG&R achieves a more profound comprehension of the intent of the code and the identification of functional defects. The IGTG&R model has been demonstrated to achieve an identification rate of functional defects ranging from 65% to 89%, with an execution success rate of 100% and a code coverage rate of 75.8%. This indicates that IGTG&R is superior to the CGTG and LLMTG approaches in multiple aspects.

Unit testing has a significant role in software development and its impacts depend on the quality of test cases and test data used. To reduce time and effort, unit test generator systems can help automatically generate test cases and test data. However, there is currently no unit test generator for Kotlin programming language even though this language is popularly used for android application developments. In this study, we propose and develop a test generator system that utilizes genetic algorithm (GA) and ANTLR4 parser. GA is used to obtain the most optimal test cases and data for a given Kotlin code. ANTLR4 parser is used to optimize the mutation process in GA so that the mutation process is not totally random. Our model results showed that the average value of code coverage in generated unit tests against instruction coverage is 95.64%, with branch coverage of 76.19% and line coverage of 96.87%. In addition, only two out of eight generated classes produced duplicate test cases with a maximum of one duplication in each class. Therefore, it can be concluded that our optimization with GA on the unit test generator is able to produce unit tests with high code coverage and low duplication.

Context: Software testing ensures software quality, but developers often disregard it. The use of automated testing generation is pursued to reduce the consequences of overlooked test cases in a software project. Problem: In the context of Java programs, several tools can completely automate generating unit test sets. Additionally, studies are conducted to offer evidence regarding the quality of the generated test sets. However, it is worth noting that these tools rely on machine learning and other AI algorithms rather than incorporating the latest advancements in Large Language Models (LLMs). Solution: This work aims to evaluate the quality of Java unit tests generated by an OpenAI LLM algorithm, using metrics like code coverage and mutation test score. Method: For this study, 33 programs used by other researchers in the field of automated test generation were selected. This approach was employed to establish a baseline for comparison purposes. For each program, 33 unit test sets were generated automatically, without human interference, by changing Open AI API parameters. After executing each test set, metrics such as code line coverage, mutation score, and success rate of test execution were collected to evaluate the efficiency and effectiveness of each set. Summary of Results: Our findings revealed that the OpenAI LLM test set demonstrated similar performance across all evaluated aspects compared to traditional automated Java test generation tools used in the previous research. These results are particularly remarkable considering the simplicity of the experiment and the fact that the generated test code did not undergo human analysis.

Automated unit test generation has been widely studied, with Large Language Models (LLMs) recently showing significant potential. LLMs like GPT-4, trained in vast text and code data, excel in various code-related tasks, including unit test generation. However, existing LLM-based approaches often focus solely on the context within the code itself, such as referenced variables, while neglecting broader task-specific contexts, such as the utility of referring to existing tests of relevant methods in unit test generation. Moreover, in the context of unit test generation, these tools prioritize high code coverage, often at the expense of practical usability, correctness, and maintainability. In response, we propose Reference-Based Retrieval Augmentation , a novel mechanism that extends LLM-based Retrieval-Augmented Generation (RAG) to retrieve relevant information by considering task-specific context. In the unit test generation task, for a given focal method, the reference relationships is defined as the reusability or referentiality of tests between the focal method and other methods. To generate high-quality unit tests for the focal method, the test reference relationships are then used to retrieve relevant methods and their existing unit tests. Specifically, we account for the unique structure of unit tests by dividing the test generation process into Given , When , and Then phases. When generating unit tests for a focal method, we retrieve pre-existing tests of other relevant methods, which can provide valuable insights for any of the Given , When , and Then phases. We implement this approach in a tool called RefTest , which sequentially performs preprocessing, test reference retrieval, and unit test generation, using an incremental strategy in which newly generated tests guide the creation of subsequent ones. We evaluated RefTest on 12 open-source projects with 1515 methods, and the results demonstrate that RefTest consistently outperforms existing tools in terms of correctness, completeness, and maintainability of the generated tests.

Recently, Large Language Models (LLMs) have shown promising results in code generation, and several automated test generation approaches based on LLMs have been proposed. Although these approaches achieve promising performance, they suffer from two limitations. First, they lack the intrinsic understanding of the semantic intricacies and logical constructs inherent to the focal method. Second, they ignore the diversity of the generated tests and generate tests with limited code coverage. To alleviate these two limitations, in this work, we propose a novel approach named TestCTRL that optimizes LLMs for unit test generation by the Chain-of-Thought (CoT) prompt and Reinforcement Learning (RL) strategy. Specifically, we first build a new CoT dataset, containing the focal methods, corresponding unit tests, and CoT prompts. The CoT prompt includes the intention and possible test input values. Then, the CoT dataset is used to fine-tune one LLM (i.e., CodeLlama 7B) that can be seen as the policy model in RL. Meanwhile, we fine-tune another LLM (i.e., CodeGPT) as the reward model by predicting the line coverage of the focal method and its test. Moreover, we employ the Proximal Policy Optimization (PPO) algorithm to optimize the policy model and generate unit tests. We use the Defects4J benchmark to evaluate our approach from three perspectives (i.e., naturalness, validity, and code coverage). To avoid data leakage threats, we filtered out data from the CoT dataset that have the same focal method and test case names as those in the Defects4J. The experimental results demonstrate that TestCTRL outperforms state-of-the-art baselines in line and branch coverages, respectively. Besides, TestCTRL improves bug detection performance. We also investigate the reason for the proposed approach’s superiority.

Testing multithreaded code is hard and expensive. Each multithreaded unit test creates two or more threads, each executing one or more methods on shared objects of the class under test. Such unit tests can be generated at random, but basic generation produces tests that are either slow or do not trigger concurrency bugs. Worse, such tests have many false alarms, which require human effort to filter out. We present BALLERINA, a novel technique for automatic generation of efficient multithreaded random tests that effectively trigger concurrency bugs. BALLERINA makes tests efficient by having only two threads, each executing a single, randomly selected method. BALLERINA increases chances that such a simple parallel code finds bugs by appending it to more complex, randomly generated sequential code. We also propose a clustering technique to reduce the manual effort in inspecting failures of automatically generated multithreaded tests. We evaluate BALLERINA on 14 real-world bugs from 6 popular codebases: Groovy, Java JDK, jFreeChart, Log4j, Lucene, and Pool. The experiments show that tests generated by BALLERINA can find bugs on average 2X-10X faster than various configurations of basic random generation, and our clustering technique reduces the number of inspected failures on average 4X-8X. Using BALLERINA, we found three previously unknown bugs in Apache Pool and Log4j, one of which was already confirmed and fixed.

Many different techniques and tools for automated unit test generation target the Java programming languages due to its popularity. However, a lot of Java’s popularity is due to its usage to develop enterprise applications with frameworks such as Java Enterprise Edition (JEE) or Spring. These frameworks pose challenges to the automatic generation of JUnit tests. In particular, code units (“beans”) are handled by external web containers (e.g., WildFly and GlassFish). Without considering how web containers initialize these beans, automatically generated unit tests would not represent valid scenarios and would be of little use. For example, common issues of bean initialization are dependency injection, database connection, and JNDI bean lookup. In this paper, we extend the EvoSuite search-based JUnit test generation tool to provide initial support for JEE applications. Experiments on 247 classes (the JBoss EAP tutorial examples) reveal an increase in code coverage, and demonstrate that our techniques prevent the generation of useless tests (e.g., tests where dependencies are not injected).

Unit testing plays an essential role in detecting bugs in functionally-discrete program units ( e.g. , methods). Manually writing high-quality unit tests is time-consuming and laborious. Although the traditional techniques are able to generate tests with reasonable coverage, they are shown to exhibit low readability and still cannot be directly adopted by developers in practice. Recent work has shown the large potential of large language models (LLMs) in unit test generation. By being pre-trained on a massive developer-written code corpus, the models are capable of generating more human-like and meaningful test code. In this work, we perform the first empirical study to evaluate the capability of ChatGPT ( i.e ., one of the most representative LLMs with outstanding performance in code generation and comprehension) in unit test generation. In particular, we conduct both a quantitative analysis and a user study to systematically investigate the quality of its generated tests in terms of correctness, sufficiency, readability, and usability. We find that the tests generated by ChatGPT still suffer from correctness issues, including diverse compilation errors and execution failures (mostly caused by incorrect assertions); but the passing tests generated by ChatGPT almost resemble manually-written tests by achieving comparable coverage, readability, and even sometimes developers’ preference. Our findings indicate that generating unit tests with ChatGPT could be very promising if the correctness of its generated tests could be further improved. Inspired by our findings above, we further propose ChatTester , a novel ChatGPT-based unit test generation approach, which leverages ChatGPT itself to improve the quality of its generated tests. Chat Tester incorporates an initial test generator and an iterative test refiner. Our evaluation demonstrates the effectiveness of ChatTester by generating 34.3 % more compilable tests and 18.7 % more tests with correct assertions than the default ChatGPT. In addition to ChatGPT, we further investigate the generalization capabilities of ChatTester by applying it to two recent open-source LLMs ( i.e. , CodeLlama-Instruct and CodeFuse) and our results show that ChatTester can also improve the quality of tests generated by these LLMs.

Automated test generation can reduce the manual effort to improve software quality. A test generation method employs code coverage, such as the widely-used branch coverage, to guide the inference of test cases. These test cases can be used to detect hidden faults. An automatic tool takes a specific type of code coverage as a configurable parameter. Given an automated tool of test generation, a fault may be detected by one type of code coverage, but omitted by another. In frequently released software projects, the time budget of testing is limited. Configuring code coverage for a testing tool can effectively improve the quality of projects. In this paper, we conduct a preliminary study on whether a fault can be detected by specific code coverage in automated test generation. We build predictive models with 60 metrics of faulty source code to identify detectable faults under eight types of code coverage, such as branch coverage. In the experiment, an off-the-shelf tool, EvoSuite is used to generate test data. Experimental results show that different types of code coverage result in the detection of different faults. The extracted metrics of faulty source code can be used to predict whether a fault can be detected with the given code coverage; all studied code coverage can increase the number of detected faults that are missed by the widely-used branch coverage. This study can be viewed as a preliminary result to support the configuration of code coverage in the application of automated test generation.

Can this fault be detected: A study on fault detection via automated test generation

Software testing is a critical activity in the software development cycle since it confirms code correctness, reliability, and maintainability. Unit testing, a cornerstone of software testing, involves verifying the correctness of individual components of a program. Manually writing these tests is a resource-intensive and time-consuming activity. Researchers have proposed various automated test generation methods to reduce the possibility of this problem. Large Language Models (LLMs) have demonstrated remarkable efficacy in automatically generating unit tests in recent years. Although a single LLM configuration can produce a satisfactory response, there are possible risks to the effectiveness of the generated tests, such as the repetition of specific test cases, the lack of edge case coverage, and the omission of full assertions. We present a novel method, LLM Chaining, that uses the collaboration of several LLMs, namely Gemini, GPT-4o, and Claude-3.5 Sonnet, to collaborate and iteratively enhance tests. We started by looking into a single LLM writing unit test, but after seeing how well they performed, we looked into LLM chaining as a way to increase the accuracy and comprehensiveness of the tests that were produced. Gemini and GPT-4o yielded the most reliable results of all the configurations we tested. Under this configuration, the LLM system uses Gemini to generate the initial JUnit tests, then sends the generated results to GPT-4o for assimilation of accuracy and depth. The HumanEval dataset was used to create JUnit test cases for this study. JaCoCo was used to collect coverage statistics, and PIT (Pitest) was used for mutation-based testing to gauge an LLM’s capacity to identify test flaws. With 99.05% branch coverage, 90.48% line coverage from 3508 test runs, and 94.32% mutation coverage, we achieved genuinely impressive results. In contrast, under the same circumstances, Randoop, a well-known automated test generation tool, obtained 68.64% branch coverage and 78.84% line coverage. This demonstrates how multi-step LLM refinement works well to advance automated test generation and, in the end, produce software that is more dependable and maintainable.

The quality of software is closely tied to the effectiveness of the tests it undergoes. Manual test writing, though crucial for bug detection, is time-consuming, which has driven significant research into automated test case generation. However, current methods often struggle to generate relevant inputs, limiting the effectiveness of the tests produced. To address this, we introduce BRMiner, a novel approach that leverages Large Language Models (LLMs) in combination with traditional techniques to extract relevant inputs from bug reports, thereby enhancing automated test generation tools. In this study, we evaluate BRMiner using the Defects4J benchmark and test generation tools such as EvoSuite and Randoop. Our results demonstrate that BRMiner achieves a Relevant Input Rate (RIR) of 60.03% and a Relevant Input Extraction Accuracy Rate (RIEAR) of 31.71%, significantly outperforming methods that rely on LLMs alone. The integration of BRMiner’s input enhances EvoSuite ability to generate more effective test, leading to increased code coverage, with gains observed in branch, instruction, method, and line coverage across multiple projects. Furthermore, BRMiner facilitated the detection of 58 unique bugs, including those that were missed by traditional baseline approaches. Overall, BRMiner’s combination of LLM filtering with traditional input extraction techniques significantly improves the relevance and effectiveness of automated test generation, advancing the detection of bugs and enhancing code coverage, thereby contributing to higher-quality software development.

Software energy consumption is a performance related non-functional requirement that complicates building software on mobile devices today. Energy hogging applications (apps) are a liability to both the end-user and software developer. Measuring software energy consumption is non-trivial, requiring both equipment and expertise, yet researchers have found that software energy consumption can be modelled. Prior works have hinted that with more energy measurement data we can make more accurate energy models. This data, however, was expensive to extract because it required energy measurement of running test cases (rare) or time consuming manually written tests. In this paper, we show that automatic random test generation with resource-utilization heuristics can be used successfully to build accurate software energy consumption models. Code coverage, although well-known as a heuristic for generating and selecting tests in traditional software testing, performs poorly at selecting energy hungry tests. We propose an accurate software energy model, GreenScaler, that is built on random tests with CPU-utilization as the test selection heuristic. GreenScaler not only accurately estimates energy consumption for randomly generated tests, but also for meaningful developer written tests. Also, the produced models are very accurate in detecting energy regressions between versions of the same app. This is directly helpful for the app developers who want to know if a change in the source code, for example, is harmful for the total energy consumption. We also show that developers can use GreenScaler to select the most energy efficient API when multiple APIs are available for solving the same problem. Researchers can also use our test generation methodology to further study how to build more accurate software energy models.