Assessing mock classes: an empirical study

• Autor(a) principal: Gustavo Henrique Alves Pereira
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Institucional da UFMG
• Texto Completo: http://hdl.handle.net/1843/39045
• topic: Software engineering; Software testing; Test doubles; Computação – Teses; Software – Testes –Teses; Software – Validação – Teses; Framework (Programa de computador) – Teses

During testing activities, developers frequently rely on dependencies that make the test harder to be implemented. In this scenario, they can use mock objects to emulate the dependencies’ behavior, which contributes to make the test fast and isolated. In practice, the emulated dependency can be dynamically created with the support of mocking frameworks or manually hand-coded in mock classes. While the former is well-explored by the research literature, the latter lacks further empirical analysis. Assessing mock classes would provide the basis to better understand how those mocks are created and consumed by developers and to detect novel practices and challenges. In this dissertation, we propose an empirical and a survey study to assess mock classes. We analyze popular Java software projects, detect over 600 mock classes, and assess their content, design, evolution, and usage. We also conduct a survey with 39 developers who maintained mock classes to better understand usage motivations. We find that mock classes: often emulate domain objects, external dependencies, and web services; are typically part of a hierarchy; are mostly public (but 1/3 are private); and are largely consumed by client projects, particularly to support web testing. Developers argue that mocking frameworks may reduce code quality and have limitations, while mock classes may improve code quality and are simple to set up in tests. Moreover, developers state several reasons to create mock classes, for example, for complex testing and to support reuse; mocking frameworks should ideally be used to create simple unit tests, but also to test external entities and to test code with minimal change. The overall perception is that the usage of mock classes is preferable over mocking frameworks, however, there are specific cases in which mocking frameworks are a better choice. Finally, we provide implications and insights to researchers and practitioners working with mock classes.