Analysis of Mutation Operators for the Python Language

A mutation introduced into a source code of a dynamically typed program can generate an incompetent mutant. Such a mutant manifests a typerelated error that cannot be detected before the mutant execution. To avoid this problem, a program mutation can be provided at run-time, or incompetent mutants should be automatically detected and eliminated. We showed that the latter solution can effectively be applied providing selected mutation operators. This paper discusses mutation operators to be used for mutation testing of Python programs. Standard and object-oriented mutation operators were applied to the Python language. Python-related operators dealing with decorators and collection slices were proposed. The operators were implemented in MutPy, the tool for mutation testing of Python programs, and experimentally evaluated.