BobH wrote:
I am changing a 50-amp breaker to a 30-amp one to install an oven that
draws less current than the old one did. I have seen information here
about testing a bad circuit breaker, but how do you test a good one? In
other words, if I install a new breaker, how do I know it will trip if
the load exceeds 30 amps?

There is no need to change the breaker to match the load, as long as
all the associated wiring is rated for 50A.

Dave