Both elements can go bad at the same time and is the most common failure.
You can test them with ohmn meter and will need to remove the switch cover(s) to access the wires to the elements.
According to the service manual the specs are,
Green/Blue wire to Green= 6.3 to 7.7 ohmns
Green/Black wire to Yellow = 12.6 to 15.4 ohmns.
Truth be told through your looking for an open circuit and when they fail they usually will not have continuity when you measure them.