The influence digital circuits produced in our society during recent years has increased incredibly. Currently they play a key role in many fields of our everyday life, especially into safety critical systems. These systems have the properties to really threaten the environment and the human life if they don’t behave properly: examples can be found in the automotive and aerospace domains. This is the reason why they must be compliant with strict protocols aiming to ensure really low probabilities of anomalies leading to catastrophic consequences. These protocols are based on several factors among which testing, that must be performed heavily and often, and whose coverage must reach extremely high percentages.