This always causes an "Ah-Shit" statement (verbal or not).
With the Emergency Light Switch left in the "ARM" position on a down-powered aircraft...... what's going to be on? Is the battery dead?
In this case, the system "did" pass a self test.
The question always arises is if the emergency light battery(s) charge on ground service power. No they don't!! This can be quite a problem during the summer's heat. Leaving an aircraft on full power with no or limited ground cooling usually will leave you with a whole bunch more problems than just the emergency lights.
The battery pack(s) charge pretty quickly. On a usual basis, you'll find they are completely charged within an hour (just about the time of a crew's pre-flight).
If this aircraft's emergency light system did not pass the self test, I would of cranked the APU for cooling and let it sit for an hour+. If it still failed...... a battery replacement would be needed.
Actual charging power on the MD-10/11 is the 115VAC-R Emergency "B Phase" bus. (Not powered on ground service power.)
On the A300-600 it is the Norm-Bus1 115VAC bus. (Not powered on ground service power)