In managed languages, serialization of objects is typically done in bespoke binary formats such as Protobuf, or markup languages such as XML or JSON. The major limitation of these formats is readability. Human developers cannot read binary code, and in most cases, suffer from the syntax of XML or JSON. This is a major issue when objects are meant to be embedded and read in source code, such as in test cases. To address this problem, we propose plain-code serialization. Our core idea is to serialize objects observed at runtime in the native syntax of a programming language. We realize this vision in the context of Java, and demonstrate a prototype which serializes Java objects to Java source code. The resulting source faithfully reconstructs the objects seen at runtime. Our prototype is called ProDJ and is publicly available. We experiment with ProDJ to successfully plain-code serialize 174,699 objects observed during the execution of 4 open-source Java applications. Our performance measurement shows that the performance impact is not noticeable. Through a user study, we demonstrate that developers prefer plain-code serialized objects within automatically generated tests over their representations as XML or JSON.

JavaScript packages are notoriously prone to bloat, a factor that significantly impacts the performance and maintainability of web applications. While web bundlers and tree-shaking can mitigate this issue in client-side applications, state-of-the-art techniques have limitations on the detection and removal of bloat in server-side applications. In this paper, we present the first study to investigate bloated dependencies within server-side JavaScript applications, focusing on those built with the widely used and highly dynamic CommonJS module system. We propose a trace-based dynamic analysis that monitors the OS file system, to determine which dependencies are not accessed during runtime. To evaluate our approach, we curate an original dataset of 91 CommonJS packages with a total of 50,488 dependencies. Compared to the state-of-the-art dynamic and static approaches, our trace-based analysis demonstrates higher accuracy in detecting bloated dependencies. Our analysis identifies 50.6% of the 50,488 dependencies as bloated: 13.8% of direct dependencies and 51.3% of indirect dependencies. Furthermore, removing only the direct bloated dependencies by cleaning the dependency configuration file can remove a significant share of unnecessary bloated indirect dependencies while preserving function correctness.

Typically, a conventional unit test (CUT) verifies the expected behavior of the unit under test through one specific input / output pair. In contrast, a parameterized unit test (PUT) receives a set of inputs as arguments, and contains assertions that are expected to hold true for all these inputs. PUTs increase test quality, as they assess correctness on a broad scope of inputs and behaviors. However, defining assertions over a set of inputs is a hard task for developers, which limits the adoption of PUTs in practice. In this paper, we address the problem of finding oracles for PUTs that hold over multiple inputs. We design a system called PROZE, that generates PUTs by identifying developer-written assertions that are valid for more than one test input. We implement our approach as a two-step methodology: first, at runtime, we collect inputs for a target method that is invoked within a CUT; next, we isolate the valid assertions of the CUT to be used within a PUT. We evaluate our approach against 5 real-world Java modules, and collect valid inputs for 128 target methods, from test and field executions. We generate 2,287 PUTs, which invoke the target methods with a significantly larger number of test inputs than the original CUTs. We execute the PUTs and find 217 that provably demonstrate that their oracles hold for a larger range of inputs than envisioned by the developers. From a testing theory perspective, our results show that developers express assertions within CUTs, which actually hold beyond one particular input.

Mocking allows testing program units in isolation. A developer who writes tests with mocks faces two challenges: design realistic interactions between a unit and its environment; and understand the expected impact of these interactions on the behavior of the unit. In this paper, we propose to monitor an application in production to generate tests that mimic realistic execution scenarios through mocks. Our approach operates in three phases. First, we instrument a set of target methods for which we want to generate tests, as well as the methods that they invoke, which we refer to as mockable method calls. Second, in production, we collect data about the context in which target methods are invoked, as well as the parameters and the returned value for each mockable method call. Third, offline, we analyze the production data to generate test cases with realistic inputs and mock interactions. The approach is automated and implemented in an open-source tool calledrick. We evaluate our approach with three real-world, open-source Java applications.rickmonitors the invocation of$128$methods in production across the three applications and captures their behavior. Based on this captured data,rickgenerates test cases that include realistic initial states and test inputs, as well as mocks and stubs. All the generated test cases are executable, and$52.4\%$of them successfully mimic the complete execution context of the target methods observed in production. The mock-based oracles are also effective at detecting regressions within the target methods, complementing each other in their fault-finding ability. We interview$5$developers from the industry who confirm the relevance of using production observations to design mocks and stubs. Our experimental findings clearly demonstrate the feasibility and added value of generating mocks from production interactions.

Test doubles, such as mocks and stubs, are nifty fixtures in unit tests. They allow developers to test individual components in isolation from others that lie within or outside of the system. However, implementing test doubles within tests is not straightforward. With this demonstration, we introduce RICK, a tool that observes executing applications in order to automatically generate tests with realistic mocks and stubs. RICK monitors the invocation of target methods and their interactions with external components. Based on the data collected from these observations, RICK produces unit tests with mocks, stubs, and mock-based oracles. We highlight the capabilities of RICK, and how it can be used with real-world Java applications, to generate tests with mocks.

Large-scale code reuse significantly reduces both development costs and time. However, the massive share of third-party code in software projects poses new challenges, especially in terms of maintenance and security. In this paper, we propose a novel technique to specialize dependencies of Java projects, based on their actual usage. Given a project and its dependencies, we systematically identify the subset of each dependency that is necessary to build the project, and we remove the rest. As a result of this process, we package each specialized dependency in aJARfile. Then, we generate specialized dependency trees where the original dependencies are replaced by the specialized versions. This allows building the project with significantly less third-party code than the original. As a result, the specialized dependencies become a first-class concept in the software supply chain, rather than a transient artifact in an optimizing compiler toolchain. We implement our technique in a tool calledDepTrim, which we evaluate with 30 notable open-source Java projects.DepTrimspecializes a total of 343 (86.6%) dependencies across these projects, and successfully rebuilds each project with a specialized dependency tree. Moreover, through this specialization,DepTrimremoves a total of 57,444 (42.2%) classes from the dependencies, reducing the ratio of dependency classes to project classes from 8.7$\boldsymbol{\times}$in the original projects to 5.0$\boldsymbol{\times}$after specialization. These novel results indicate that dependency specialization significantly reduces the share of third-party code in Java projects.

GraphQL is a new paradigm to design web APIs. Despite its growing popularity, there are few techniques to verify the implementation of a GraphQL API. We present a new testing approach based on GraphQL queries that are logged while users interact with an application in production. Our core motivation is that production queries capture real usages of the application, and are known to trigger behavior that may not be tested by developers. For each logged query, a test is generated to assert the validity of the GraphQL response with respect to the schema. We implement our approach in a tool called AutoGraphQL, and evaluate it on two real-world case studies that are diverse in their domain and technology stack: an open-source e-commerce application implemented in Python called Saleor, and an industrial case study which is a PHP-based finance website called Frontapp. AutoGraphQL successfully generates test cases for the two applications. The generated tests cover 26.9 % of the Saleor schema, including parts of the API not exercised by the original test suite, as well as 48.7% of the Frontapp schema, detecting 8 schema faults, thanks to production queries.

In this article, we propose to use production executions to improve the quality of testing for certain methods of interest for developers. These methods can be methods that are not covered by the existing test suite or methods that are poorly tested. We devise an approach calledpanktiwhich monitors applications as they execute in production and then automatically generates differential unit tests, as well as derived oracles, from the collected data.pankti’s monitoring and generation focuses on one single programming language, Java. We evaluate it on three real-world, open-source projects: a videoconferencing system, a PDF manipulation library, and an e-commerce application. We show thatpanktiis able to generate differential unit tests by monitoring target methods in production and that the generated tests improve the quality of the test suite of the application under consideration.