Special features of process control expert systems (PCX) make it both
necessary and feasible to test them in a comprehensive manner. FAITH,
an automated regression testing environment for PCX, integrates five s
pecially adapted testing techniques, exploiting external specification
s gained from the process control environment. FAITH also offers a set
of metrics which can be used to predict testability during the early
phases of PCX development. FAITH has been developed for a major German
chemicals company where it is routinely used for certifying PCX, and
for guiding design-for-testability.