A Simple and Practical Approach to Unit Testing: The JML and JUnit Way

Writing unit test code is labor-intensive, hence it is often not done as an integral part of programming. However, unit testing is a practical approach to increasing the correctness and quality of software; for example, the Extreme Programming approach relies on frequent unit testing. In this paper we present a new approach that makes writing unit tests easier. It uses a formal specification language\u27s runtime assertion checker to decide whether methods are working correctly, thus automating the writing of unit test oracles. These oracles can be easily combined with hand-written test data. Instead of writing testing code, the programmer writes formal specifications (e.g., pre- and postconditions). This makes the programmer\u27s task easier, because specifications are more concise and abstract than the equivalent test code, and hence more readable and maintainable. Furthermore, by using specifications in testing, specification errors are quickly discovered, so the specifications are more likely to provide useful documentation and inputs to other tools. We have implemented this idea using the Java Modeling Language (JML) and the JUnit testing framework, but the approach could be easily implemented with other combinations of formal specification languages and unit test tools

A Simple and Practical Approach to Unit Testing: The JML and JUnit Way

Writing unit test code is labor-intensive, hence it is often not done as an integral part of programming. However, unit testing is a practical approach to increasing the correctness and quality of software; for example, the Extreme Programming approach relies on frequent unit testing. In this paper we present a new approach that makes writing unit tests easier. It uses a formal specification language\u27s runtime assertion checker to decide whether methods are working correctly, thus automating the writing of unit test oracles. These oracles can be easily combined with hand-written test data. Instead of writing testing code, the programmer writes formal specifications (e.g., pre- and postconditions). This makes the programmer\u27s task easier, because specifications are more concise and abstract than the equivalent test code, and hence more readable and maintainable. Furthermore, by using specifications in testing, specification errors are quickly discovered, so the specifications are more likely to provide useful documentation and inputs to other tools. We have implemented this idea using the Java Modeling Language (JML) and the JUnit testing framework, but the approach could be easily implemented with other combinations of formal specification languages and unit test tools

The JML and JUnit Way of Unit Testing and its Implementation

Writing unit test code is labor-intensive, hence it is often not done as an integral part of programming. However, unit testing is a practical approach to increasing the correctness and quality of software; for example, Extreme Programming relies on frequent unit testing. In this paper we present a new approach that makes writing unit tests easier. It uses a formal specification language\u27s runtime assertion checker to decide whether methods are working correctly; thus code to decide whether tests pass or fail is automatically produced from specifications. Our tool combines this testing code with hand-written test data to execute tests. Therefore, instead of writing testing code, the programmer writes formal specifications (e.g., pre- and postconditions). This makes the programmer\u27s task easier, because specifications are more concise and abstract than the equivalent test code, and hence more readable and maintainable. Furthermore, by using specifications in testing, specification errors are quickly discovered, so the specifications are more likely to provide useful documentation and inputs to other tools. In this paper we describe an implementation using the Java Modeling Language (JML) and the JUnit testing framework, but the approach could be easily implemented with other combinations of formal specification languages and unit testing tools

An Empirical Evaluation of the Effectiveness of JML Assertions as Test Oracles

Test oracles remain one of the least understood aspects of the modern testing process. An oracle is a mechanism used by software testers and software engineers for determining whether a test has passed or failed. One widely-supported approach to oracles is the use of runtime assertion checking during the testing activity. Method invariants,pre- and postconditions help detect bugs during runtime. While assertions are supported by virtually all programming environments, are used widely in practice, and are often assumed to be effective as test oracles, there are few empirical studies of their efficacy in this role. In this thesis, we present the results of an experiment we conducted to help understand this question. To do this, we studied seven of the core Java classes that had been annotated by others with assertions in the Java Modeling Language, used the muJava mutation analysis tool to create mutant implementations of these classes, exercised them with input-only (i.e., no oracle) test suites that achieve branch coverage, and used a machine learning tool, Weka, to determine which annotations were effective at ``killing\u27\u27 these mutants. We also evaluate how effective the ``null oracle\u27\u27 (in our case, the Java runtime system) is at catching these bugs. The results of our study are interesting, and help provide software engineers with insight into situations in which assertions can be relied upon to find bugs, and situations in which assertions may need to be augmented with other approaches to test oracles

Design by Contract Using Meta-Assertions

The important role that class contracts - pre and post-conditions of methods, and invariants - play in the specification, monitoring and reuse of classes is becoming increasingly accepted by the OO community. The several languages of assertions and monitoring code generation tools that exist allow the specification and, eventually, the runtime checking of very powerful and elegant contracts. This is definitely so for classes as simple as Stack, Point or Account. However, when the aim is the writing of pre and post-conditions for methods in classes that are clients of those simple classes, the task reveals itself harder and brings undesirable effects, like the increasing in class coupling and encapsulation decreasing. In addition, the conviction that assertions should have no side effects in order to be possible to monitor them, weakens the expressive power of assertion languages and makes it more difficult to avoid the above mentioned undesirable effects. In this paper we propose a pattern to the design of class contracts that is an adaptation of existing patterns of design into a declarative context - the world of assertions. The use of this pattern produces contracts that preserve low class coupling and data encapsulation. The expressive power of existing assertion languages is insufficient, however, to write these contracts. In order to fill this lack, we propose meta-assertions and formally define their syntax and semantics. In order to be possible to check contracts at runtime, we define rules for the expansion of meta-assertions that can be monitored by existing tools, and we show grammatical and semantic soundness of the expansio

OCL exception handling

Object Constraint Language (OCL) is part of the Unified Modeling Language (UML) specification and can be used to enforce constraints on the attributes or methods of a class. It would greatly help the software developers if such non-executable OCL constraints specified in a UML model could be enforced on the executable code generated from the model. This thesis discusses the concepts, ideas and the approach in transforming a model developed in the Rational Rose software with OCL constraints into Java code shells, complete with fragments of code to detect the run-time violations of the constraints. The implementation and testing of a prototype tool that incorporates these ideas is also discussed

SAVCBS 2004 Specification and Verification of Component-Based Systems: Workshop Proceedings

This is the proceedings of the 2004 SAVCBS workshop. The workshop is concerned with how formal (i.e., mathematical) techniques can be or should be used to establish a suitable foundation for the specification and verification of component-based systems. Component-based systems are a growing concern for the software engineering community. Specification and reasoning techniques are urgently needed to permit composition of systems from components. Component-based specification and verification is also vital for scaling advanced verification techniques such as extended static analysis and model checking to the size of real systems. The workshop considers formalization of both functional and non-functional behavior, such as performance or reliability

SAVCBS 2001 Proceedings: Specification and Verification of Component-Based Systems, Workshop at OOPSLA 2001

The goal of this workshop was to explore how formal (i.e., mathematical) techniques can be or should be used to establish a suitable foundation for specification and verification of component-based systems. Component-based systems are a growing concern for the object-oriented community. Specification and reasoning techniques are urgently needed to permit composition of systems from components, for which source code is unavailable. This report is the proceedings of the worksho