yagg: an easy-to-use generator for structured test inputs

Automated testing typically uses specifications to drive the generation of test inputs and/or the checking of program outputs. Many software systems have structurally complex inputs that cannot be adequately described using simple formalisms such as context-free grammars. In order to generate such inputs, many automated testing environments require the user to express the structure of the input using an unfamiliar formal notation. This raises the cost of employing automated testing, thereby offsetting the benefits gained. We present yagg (yet another generator-generator), a tool that allows the programmer to specify the input using a syntax very similar to that of LEX and YACC, widely used scanner and parser generators. yagg allows the user to bound the input space using several different techniques, and generates an input generator that systematically enumerates inputs. We evaluate the ease of use and performance of the tool relative to a model checker-based generator used in previous research. Our experiences indicate that yagg generators can be somewhat slower, but that the ease-of-use afforded by the familiar syntax may be attractive to users.