Code refactoring is supported by many Integrated Development Environments.This paper is focused on the automated code refactoring of C# programs.We have analyzed more than sixty refactorings available in three popular IDEs.We cataloged different restrictions, defects, and other quality concerns associated with the implementation of the refactorings, taking into account both modification of the production code and of the corresponding test cases.An extension to automate selected refactoring improvements has been developed for the ReSharper platform and experimentally verified.

In Model-Driven Software Development (MDSD), an application can be built using classes and their state machines as source models. The final application can be tested as any source code. In this paper, we discuss a specific approach to mutation testing in which modifications relate to different variants of behavioural features modelled by UML state machines, while testing deals with standard executions of the final application against its test cases. We have proposed several mutation operators aimed at mutating behaviour of UML state machines. The operators take into account event processing, time management, behaviour of complex states with orthogonal regions, and usage of history pseudostates. Different possible semantic interpretations are associated with each operator. The operators have been implemented in the Framework for eXecutable UML (FXU). The framework, that supports code generation from UML classes and state machines and building target C# applications, has been extended to realize mutation testing with use of multiple libraries. The semantic mutation operators have been verified in some MDSD experiments.

Behavior of UML state machines can be a source of interpretation problems in model to code transformation.Different solutions to the semantic variants could be defined as a special kind of mutations, similarly as in the mutation testing.State machines together with class models can be a source of an Model-Driven Software Development process aimed at building an executable application.We have compared several approaches to creating applications based on models in which semantic mutation operators of state machine behavior are used.The most promising approach has been utilized to extend the Framework for eXecutable UML (FXU) with semantic mutation facilities.The framework supports code generation from UML classes and their state machines as well as developing C# applications according to selected mutations of state machine behavior.The tool has been used in evaluation of a case study.

Mutation testing of object-oriented programs differs from that of standard (traditional) mutation operators in accordance to the number of generated mutants and ability of tests to kill mutants.Therefore, outcomes of cost reduction analysis cannot be directly transferred from a standard mutation to an object-oriented one.Mutant sampling is one of reduction methods of the number of generated and tested mutants.We proposed different mutant sampling criteria based on equivalence partitioning in respect to object-oriented program features.The criteria were experimentally evaluated for object-oriented and standard mutation operators applied in C# programs.We compared results using a quality metric, which combines mutation score accuracy with mutation cost factors.In result, class random sampling and operator random sampling are recommended for OO and standard mutation testing, accordingly.With a reasonable decline of result accuracy, the mutant sampling technique is easily applicable in comparison to other cost reduction techniques.