Team, Visitors, External Collaborators
Overall Objectives
Research Program
Application Domains
Highlights of the Year
New Software and Platforms
New Results
Bilateral Contracts and Grants with Industry
Partnerships and Cooperations
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Section: New Results

Software Reengineering

Decomposing God Classes at Siemens A group of developers at Siemens Digital Industry Division approached our team to help them restructure a large legacy system. Several problems were identified, including the presence of God classes (big classes with thousands of lines of code and hundred of methods). They had tried different approaches considering the dependencies between the classes, but none were satisfactory. Through interaction during the last three years with a lead software architect of the project, we designed a software visualization tool and an accompanying process that allows her to propose a decomposition of a God Class in a matter of one or two hours even without prior knowledge of the class (although actually implementing the decomposition in the source code could take a week of work). We present the process that was formalized to decompose God Classes and the tool that was designed. We give details on the system itself and some of the classes that were decomposed. The presented process and visualisations have been successfully used for the last three years on a real industrial system at Siemens. [1]

Rotten Green Tests Unit tests are a tenant of agile programming methodologies, and are widely used to improve code quality and prevent code regression. A green (passing) test is usually taken as a robust sign that the code under test is valid. However, some green tests contain assertions that are never executed. We call such tests Rotten Green Tests. Rotten Green Tests represent a case worse than a broken test: they report that the code under test is valid, but in fact do not test that validity. We describe an approach to identify rotten green tests by combining simple static and dynamic call-site analyses. Our approach takes into account test helper methods, inherited helpers, and trait compositions, and has been implemented in a tool called DrTest. DrTest reports no false negatives, yet it still reports some false positives due to conditional use or multiple test contexts. Using DrTest we conducted an empirical evaluation of 19,905 real test cases in mature projects of the Pharo ecosystem. The results of the evaluation show that the tool is effective; it detected 294 tests as rotten-green tests that contain assertions that are not executed. Some rotten tests have been "sleeping" in Pharo for at least 5 years. [2]

Migrating GWT to Angular 6 using MDE In the context of a collaboration with Berger-Levrault, a major IT company, we are working on the migration of a GWT application to Angular. We focus on the GUI aspect of this migration which, even if both are web frameworks, is made difficult because they use different programming languages (Java for one, Typescript for the other) and different organization schemas (e.g. different XML files). Moreover, the new application must mimic closely the visual aspect of the old one so that the users of the application are not disturbed. We propose an approach in three steps that uses a meta-model to represent the GUI at a high abstraction level. We evaluated this approach on an application comprising 470 Java (GWT) classes representing 56 screens. We are able to model all the web pages of the application and 93% of the wid-gets they contain, and we successfully migrated (i.e., the result is visually equal to the original) 26 out of 39 pages (66%). We give examples of the migrated pages, both successful and not. [14] [11] [12]

Empirical Study of Programming to an Interface A popular recommendation to programmers in object-oriented software is to program to an interface, not an implementation (PTI). Expected benefits include increased simplicity from abstraction, decreased dependency on implementations, and higher flexibility. Yet, interfaces must be immutable, excessive class hierarchies can be a form of complexity, and speculative generality is a known code smell. To advance the empirical knowledge of PTI, we conducted an empirical investigation that involves 126 Java projects on GitHub, aiming to measuring the decreased dependency benefits (in terms of cochange). [13]

Exposing Test Analysis Results with DrTests Tests are getting the cornerstone of continuous development process and software evolution. Tests are the new gold. To improve test quality, a plethora of analyses is proposed such as test smells, mutation testing, test coverage. The problem is that each analysis often needs a particular way to expose its results to the developer. There is a need for an architecture supporting test running and analysis in a modular and extensible way. We present an extensible plugin-based architecture to run and report test results. DrTests is a new test browser that implements such plugin-based architecture. DrTests supports the execution of rotten tests, comments to tests, coverage and profiling tests. [5]