Fault Injection or Fault Insertion
Fault Injection is the process of inserting errors into a system while examining the behavior of the system. By carefully selecting which errors to insert, where and when, the outcome of the assessment reveals how the system behaves in the presence of real stress / disturbance.
Fault Injection testing can demonstrate that software is unlikely to do what it shouldn't. Fault insertion offers a way to evaluate the effectiveness of false tests being performed.
Fault Injection can help to expose new output states that before have never been observed or considered.