On the Emulation of Software Faults by Software Fault Injection

This paper presents an experimental study on the emulation of software faults by fault injection. In a first experiment, a set of real software faults has been compared with faults injected by a SWIFI tool (Xception) to evaluate the accuracy of the injected faults. Results revealed the limitations of Xception (and other SWIFI tools) in the emulation of different classes of software faults (about 44% of the software faults cannot be emulated). The use of field data about real faults was discussed and software metrics were suggested as an alternative to guide the injection process when field data is not available. In a second experiment, a set of rules for the injection of errors meant to emulate classes of software faults was evaluated. The fault triggers used seem to be the cause for the observed strong impact of the faults in the target system and in the program results. The results also show the influence in the fault emulation of aspects such as code size, complexity of data structures, and recursive versus sequential execution.1