Most modern diesel-electric locomotives are capable of a self load test using their dynamics, but the primary purpose is to determine if the diesel prime mover is capable of putting out its full horsepower. The propulsion and dynamic circuits are not tested during a load test.

Modern dynamic brake systems can detect if there is an open circuit in the resistance grids or the related cooling fans.

I'm not sure to what degree modern locos can monitor their dynamic brake systems and notify the engineer if they aren't functioning as expected. There was a recommendation years ago that the engineer be able to monitor at least the dynamic brake amps of trailing units from the controlling unit, but I'm not sure that ever happened though I have heard of a similar system used on some cab cars. To my knowledge, the recommendation never was acted further on as far as becoming a regulation.

M-K now MPI track tests their new/rebuilt/repaired locos by doubleheading them, one in dynamics and one in power working them against each other.