MODIFI: A MODel-Implemented Fault Injection Tool

Fault injection is traditionally divided into simulation-based and physical techniques depending on whether faults are injected into hardware models, or into an actual physical system or prototype. Another classification is based on how fault injection mechanisms are implemented. Well known techniques are hardware-implemented fault injection (HIFI) and softwareimplemented fault injection (SWIFI). For safety analyses during model-based development, fault injection mechanisms can be added directly into models of hardware, models of software or models of systems. This approach is denoted by the authors as model-implemented fault injection. This paper presents the MODIFI (MODel-Implemented Fault Injection) tool. The tool is currently targeting behaviour models in Simulink. Fault models used by MODIFI are defined using XML according to a specific schema file and the fault injection algorithm uses the concept of minimal cut sets (MCS) generation. First, a user defined set of single faults are injected to see if the system is tolerant against single faults. Single faults leading to a failure, i.e. a safety requirement violation, are stored in a MCS list together with the corresponding counterexample. These faults are also removed from the fault space used for subsequent experiments. When all single faults have been injected, the effects of multiple faults are investigated, i.e. two or more faults are introduced at the same time. The complete list of MCS is finally used to automatically generate test cases for efficient fault injection on the target system.