Type Sensitive Application of Mutation Operators for Dynamically Typed Programs

Abstract

It is commonly accepted that strong typing is useful for revealing programmer errors and so the use of dynamically typed languages increases the importance of software testing. Mutation analysis is a demanding software testing criterion. Although mutation analysis has been applied to procedural languages, and object oriented languages, little work has been done on the mutation analysis of programs written in dynamically typed languages.Mutation analysis depends on the substitution and modification of program elements. In a strongly typed language, the declared type of the mutated element, a variable or operator, can be used to avoid generating type-incorrect substitutions or modifications. In a dynamically typed language, this type information is not available and so a much greater range of mutations are potentially applicable but many of the resulting mutants are likely to be incompetent (too easily killed). This paper describes a mutation analysis method in which the definition of mutants is performed at run-time when type information is available. The type information can be used to avoid generating incompetent mutants.

Experimental Evaluation of Mutation Testing Approaches to Python Programs

“…The problem of dynamically typed programs was addressed by Bottaci in [2]. He described the mutation analysis introduced during a mutant run-time, when information about type of program elements is available.…”

“…One of solutions towards mutation of dynamically typed programs is the mutation of a running code [2]. In this paper we focus on another approach based on the experiences with Python programs.…”

“…This condition cannot be verified in Python programs, and in other dynamically typed ones, before a mutant is run. Applying a mutation that is incorrect due to types used in a modified expression, an incompetent mutant will be created [2]. In general, incompetent mutants include also still-born mutants that can be detected by static analysis at the compilation stage.…”

Automatic Detection and Removal of Ineffective Mutants for the Mutation Analysis of Relational Database Schemas

“…Finally, mutation may introduce another type of ineffective CREATE mutant, known as the stillborn mutant. These mutants are ones where the seeded change has caused it to become invalid-for example, producing a program that does not compile [38]. Stillborn mutants slow down the process of mutation analysis, since there is an execution cost associated with finding them to be invalid (e.g., due to a compilation error) and removing them from the mutant pool so that they receive no further consideration.…”

“…In the context of program mutation, stillborn mutants are programs that do not compile due to a mutation operator making it syntactically or semantically invalid [38]. Such mutants cannot be used during mutation analysis, since they do not represent an artifact against which any tests can be run.…”