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.

This paper presents and evaluates a methodology for the emulation of software faults in COTS components using software implemented fault injection (SWIFI) technology. ESFFI (Emulation of Software Faults by Fault Injection) leverages matured fault injection techniques, which have been used so far for the emulation of hardware faults, and adds new features that make possible the insertion of errors mimicking those caused by real software faults. The major advantage of ESFFI over other techniques that also emulate software faults (mutations, for instance) is making fault locations ubiquitous; every software module can be targeted no matter if it is a device driver running in operating kernel mode or a 3 rd party component whose source code is not available. Experimental results have shown that for specific fault classes, e.g. assignment and checking, the accuracy obtained by this technique is quite good. 1.

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Sponsor: Microsoft (UK) Project funded by the European Community under the “Information Society Technologies” Programme (1998-2002) Table of Contents Abstract................................................................................................................................. 1

LAAS-CNRS (France),