This paper introduces an abstract specification of mutation operators that (1) we have used to create traditional operators and, (2) we are currently using to define and implement mutation operators for context-aware, mobile applications that come from a list of common errors reported by three companies. This specification describes the structure and behavior of mutation operators at a high abstraction level, thus supporting the specification of new mutation operators according to the evolving state of the art of context-awareness. The paper also gives some notes about BacterioWeb, a web-based mutant tool with an execution engine for Android applications.