Fault Injection (FI) is an established testing technique to assess the fault-tolerance of computer systems. FI tests are usually highly automated for efficiency and to prevent human error from affecting result reliability. Most existing FI automation tools have been built for a specific application domain, i.e., A certain system under test (SUT) and fault types to test the SUT against, which significantly restricts their reusability. To improve reusability, generalist fault injection tools have been developed to decouple SUT-independent functionality from SUT-specific code. Unfortunately, existing generalist tools often embed subtle and implicit assumptions about the target system that affect their reusability. Furthermore, no assessments have been conducted how much effort the SUT-specific adaptation of generalist tools entails in comparison to reimplementation from scratch. In this paper, we present GRINDER, an open-source, highly-reusable FI tool, and report on its applicability in two very different systems (the Android OS in an emulated environment, and a real-time AUTOSAR system) under four different FI scenarios. © 2015 IEEE.