How do you detect if a shunt trip breaker is malfunctioning?

The way to detect if a shunt trip breaker is malfunctioning is to manually trip the breaker. The shunt is usually wired through a auxiliary relay. Make sure that before you trip the breaker that the load can be shut off without taking a production line etc. off line. Trip the auxiliary relay using a test jumper to activate the relays coil. The breaker's handle will move to mid throw and the load will disconnect from the supply power. If the breaker trips then it is working properly. If the breaker does not trip trouble shoot the circuitry that is used to trip the breaker. Usual problem is an open circuit.