Many critical bugs are actually due to poor error handling [3]; by deliberately inducing faults, you ensure that the fault-tolerance machinery is continually exercised and tested, which can increase your confidence that faults will be handled correctly when they occur naturally.
A good approach can be to update your data in the master, and then just trigger your "caches are inconsistent" code.
It regularly runs and verifies your ability to recover from errors. Detecting errors in the general case can still be a problem though.
