An experimental comparison of fault and error injection

The complex interactions between faults, errors, failures and fault handling mechanisms can be studied via injection experiments. This paper presents an investigation of both fault and error injection techniques for emulating software faults. For evaluation, 1600 software faults and 5400 time-triggered errors were injected into an embedded real-time system. The cost-related results are: (i) the time required to create a fault set for fault injection was about 120 times longer than the time required to create an error set for time-triggered injection and (ii) the execution time for the time-triggered error injection experiments were four times shorther than for the fault injection experiments. However, the error injection would be only 1.3 times faster if another strategy for fault injection had been used. Furthermore, failure symptom related results are: (i) the test case had a greater influence than the fault type on the failure symptoms for fault injections, (ii) the error type had a greater influence on the failure symptom for timetriggered error injections than had the test case and (iii) the error type had a larger impact on the failure symptoms than the fault type.