Mutation testing is the art of generating syntactic versions (called mutants) of a base program, and is widely used in software testing, most notably the assessment of test suites. Mutants are useful only to the extent that they are semantically distinct from the base program, but some may well be semantically equivalent to the base program, despite being syntactically distinct. Much research has been devoted to identifying, and weeding out, equivalent mutants, but determining whether two programs are semantically equivalent is a non-trivial, tedious, error-prone task. Yet in practice it is not necessary to identify equivalent mutants individually; for most intents and purposes, it suffices to estimate their number. In this paper, we are interested to estimate, for a given number of mutants generated from a program, the ratio of those that are equivalent to the base program; we refer to this as the Ratio of Equivalent Mutants (REM, for short). We argue, on the basis of analytical grounds, that the REM of a program may be estimated from a static analysis of the program, and that it can be used to analyze many mutation related properties of a program. The purpose/ aspiration of this paper is to draw attention to this potentially cost-effective approach to a longstanding stubborn problem.

突变测试是生成基本程序的句法版本（称为突变体）的艺术，广泛用于软件测试，尤其是测试套件的评估。突变体仅在它们在语义上与基础程序不同时才有用，但有些突变体可能在语义上与基础程序等效，尽管它们在语法上是不同的。许多研究致力于识别和剔除等效的突变体，但确定两个程序在语义上是否等效是一项重要的、乏味的、容易出错的任务。然而在实践中，没有必要单独识别等效的突变体；对于大多数意图和目的，估计它们的数量就足够了。在本文中，我们有兴趣估计，对于从程序生成的给定数量的突变体，与基本程序相当的比率；我们将其称为等效突变体比率（简称 REM）。我们认为，基于分析依据，程序的 REM 可以通过对程序的静态分析来估计，并且可以用来分析程序的许多与突变相关的属性。本文的目的/愿望是引起人们对这种解决长期顽固问题的潜在成本效益方法的关注。