How functional programming mattered

In 1989 when functional programming was still considered a niche topic, Hughes wrote a visionary paper arguing convincingly ‘why functional programming matters’. More than two decades have passed. Has functional programming really mattered? Our answer is a resounding ‘Yes!’. Functional programming is now at the forefront of a new generation of programming technologies, and enjoying increasing popularity and influence. In this paper, we review the impact of functional programming, focusing on how it has changed the way we may construct programs, the way we may verify programs, and fundamentally the way we may think about programs

Automated Test Generation Based on an Applicational Model

Context: As testing is an extremely costly and time-consuming process, tools to automatically generate test cases have been proposed throughout the literature. OutSystems provides a software development environment where with the aid of the visual OutSystems language, developers can create their applications in an agile form, thus improving their productivity. Problem: As OutSystems aims at accelerating software development, automating the test case generation activity would bring great value to their clients. Objectives: The main objectives of this work are to: develop an algorithm that generates, automatically, test cases for OutSystems applications and evaluates the coverage they provide to the code, according to a set of criteria. Methods: The OutSystems language is represented as a graph to which developers can then add pieces of code by dragging nodes to the screen and connecting them to the graph. The methodology applied in this work consists in traversing these graphs with depth and breadth-first search algorithms, employing a boundary-value analysis to identify the test inputs and a cause-effect graphing to reduce the number of redundant inputs generated. To evaluate these test inputs, coverage criteria regarding the control flow of data are analysed according to node, branch, condition, modified condition-decision and multiple condition coverage. Results: This tool is able to generate test inputs that cover 100% of reachable code and the methodologies employed help greatly in reducing the inputs generated, as well as displaying a minimum set of test inputs with which the developer is already able to cover all traversable code. Usability tests also yield very optimistic feedback from users. Conclusions: This work’s objectives were fully met, seen as we have a running tool able to act upon a subset of the OutSystems applicational model. This work provides crucial information for assessing the quality of OutSystems applications, with value for OutSystems developers, in the form of efficiency and visibility

Aplicación de técnicas de pruebas automáticas basadas en propiedades a los diferentes niveles de prueba del software

[Resumen]Las pruebas son una de las actividades clave en el desarrollo de software, puesto que ayudan a detectar defectos que, de otro modo, pasarían desapercibidos hasta que el software sea desplegado. Sin embargo, al contrario que en otras etapas del ciclo de vida del software, como son el análisis, el diseño o la implementación, para las que existen metodologías y técnicas bien definidas y ampliamente aceptadas en la comunidad informática, junto con herramientas que permiten llevar a cabo dichas tareas, no hay una uniformidad sobre las metodologías, técnicas o herramientas a utilizar para llevar a cabo las pruebas del software de una manera eficiente y eficaz. Este hecho provoca que, muchas veces, éstas sean omitidas o no realizadas con todo el rigor necesario. Esta tesis presenta una aproximación, basada en propiedades y puramente funcional, para la realización de las pruebas del software, que intenta paliar estos problemas. Para ello, se definen metodologías y técnicas de pruebas, integradas en el proceso de desarrollo de software, que pueden ser aplicadas a los diferentes niveles de pruebas del software. Así, pueden utilizarse para llevar a cabo pruebas unitarias y de componente, en las que se comprueba que cada componente individual se comporta de la manera esperada, pruebas de integración, que comprueban las interacciones de los componentes que forman parte de un sistema, y pruebas de sistema, que se encargan de comprobar diferentes aspectos del sistema como un todo. Además, se utiliza un lenguaje de especificación de pruebas común en todas las aproximaciones desarrolladas, el lenguaje de programación funcional Erlang, y las metodologías se definen de manera independiente a la estructura del software concreto a probar o el lenguaje de programación en el que éste esté implementado. Por último, cabe destacar que el uso de estas metodologías y técnicas de pruebas se ilustra a través de un ejemplo industrial, en concreto, el sistema VoDKATV. Este sistema ofrece acceso a servicios multimedia (canales de televisión, videoclub, aplicaciones, juegos, entre otros) a través de diferentes tipos de dispositivos, como, por ejemplo, televisiones, ordenadores, tabletas o móviles. Con respecto a la arquitectura, el sistema VoDKATV está compuesto por múltiples componentes implementados con diferentes tecnologías (Java, Erlang, C, etc.) que se integran entre sí. La complejidad de este sistema permite ilustrar cada una de las metodologías y técnicas de pruebas desarrolladas con un ejemplo real

Towards A Practical High-Assurance Systems Programming Language

Writing correct and performant low-level systems code is a notoriously demanding job, even for experienced developers. To make the matter worse, formally reasoning about their correctness properties introduces yet another level of complexity to the task. It requires considerable expertise in both systems programming and formal verification. The development can be extremely costly due to the sheer complexity of the systems and the nuances in them, if not assisted with appropriate tools that provide abstraction and automation. Cogent is designed to alleviate the burden on developers when writing and verifying systems code. It is a high-level functional language with a certifying compiler, which automatically proves the correctness of the compiled code and also provides a purely functional abstraction of the low-level program to the developer. Equational reasoning techniques can then be used to prove functional correctness properties of the program on top of this abstract semantics, which is notably less laborious than directly verifying the C code. To make Cogent a more approachable and effective tool for developing real-world systems, we further strengthen the framework by extending the core language and its ecosystem. Specifically, we enrich the language to allow users to control the memory representation of algebraic data types, while retaining the automatic proof with a data layout refinement calculus. We repurpose existing tools in a novel way and develop an intuitive foreign function interface, which provides users a seamless experience when using Cogent in conjunction with native C. We augment the Cogent ecosystem with a property-based testing framework, which helps developers better understand the impact formal verification has on their programs and enables a progressive approach to producing high-assurance systems. Finally we explore refinement type systems, which we plan to incorporate into Cogent for more expressiveness and better integration of systems programmers with the verification process

Holistic recommender systems for software engineering

The knowledge possessed by developers is often not sufficient to overcome a programming problem. Short of talking to teammates, when available, developers often gather additional knowledge from development artifacts (e.g., project documentation), as well as online resources. The web has become an essential component in the modern developer’s daily life, providing a plethora of information from sources like forums, tutorials, Q&A websites, API documentation, and even video tutorials. Recommender Systems for Software Engineering (RSSE) provide developers with assistance to navigate the information space, automatically suggest useful items, and reduce the time required to locate the needed information. Current RSSEs consider development artifacts as containers of homogeneous information in form of pure text. However, text is a means to represent heterogeneous information provided by, for example, natural language, source code, interchange formats (e.g., XML, JSON), and stack traces. Interpreting the information from a pure textual point of view misses the intrinsic heterogeneity of the artifacts, thus leading to a reductionist approach. We propose the concept of Holistic Recommender Systems for Software Engineering (H-RSSE), i.e., RSSEs that go beyond the textual interpretation of the information contained in development artifacts. Our thesis is that modeling and aggregating information in a holistic fashion enables novel and advanced analyses of development artifacts. To validate our thesis we developed a framework to extract, model and analyze information contained in development artifacts in a reusable meta- information model. We show how RSSEs benefit from a meta-information model, since it enables customized and novel analyses built on top of our framework. The information can be thus reinterpreted from an holistic point of view, preserving its multi-dimensionality, and opening the path towards the concept of holistic recommender systems for software engineering

Automatic testing of software with structurally complex inputs

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 123-132).Modern software pervasively uses structurally complex data such as linked data structures. The standard approach to generating test suites for such software, manual generation of the inputs in the suite, is tedious and error-prone. This dissertation proposes a new approach for specifying properties of structurally complex test inputs; presents a technique that automates generation of such inputs; describes the Korat tool that implements this technique for Java; and evaluates the effectiveness of Korat in testing a set of data-structure implementations. Our approach allows the developer to describe the properties of valid test inputs using a familiar implementation language such as Java. Specifically, the user provides an imperative predicate--a piece of code that returns a truth value--that returns true if the input satisfies the required property and false otherwise. Korat implements our technique for solving imperative predicates: given a predicate and a bound on the size of the predicate's inputs, Korat automatically generates the bounded-exhaustive test suite that consists of all inputs, within the given bound, that satisfy the property identified by the predicate. To generate these inputs, Korat systematically searches the bounded input space by executing the predicate on the candidate inputs. Korat does this efficiently by pruning the search based on the predicate's executions and by generating only nonisomorphic inputs. Bounded-exhaustive testing is a methodology for testing the code on all inputs within the given small bound.(cont.) Our experiments on a set of ten linked and array- based data structures show that Korat can efficiently generate bounded-exhaustive test suites from imperative predicates even for very large input spaces. Further, these test suites can achieve high statement, branch, and mutation coverage. The use of our technique for generating structurally complex test inputs also enabled testers in industry to detect faults in real, production-quality applications.by Darko Marinov.Ph.D

Model Checking and Model-Based Testing : Improving Their Feasibility by Lazy Techniques, Parallelization, and Other Optimizations

This thesis focuses on the lightweight formal method of model-based testing for checking safety properties, and derives a new and more feasible approach. For liveness properties, dynamic testing is impossible, so feasibility is increased by specializing on an important class of properties, livelock freedom, and deriving a more feasible model checking algorithm for it. All mentioned improvements are substantiated by experiments