Plug your headphone into a. front jack and b. rear jack
Confirm any changes in Output
If yes, attach IOReg.
a:front jack (mic & headphone)
1. plugged a TRRS(L+R+Mic) headphone with mic(original earpods), output not changed, no sound.
2. plugged plugged a TRS(L+R) headphone, no sound, not changed in output.
b.rear jack (SPDIF & lineout)
1. plugged a TRRS(L+R+Mic) headphone with mic(original earpods). output not changed, no sound
2. plugged a TRS(L+R) headphone, no sound, not changed in output
Since I don't see any "refresh" button, so I only plugged and see the Pref/Audio/Output, and hit play then pause on iTunes.
And now can simply call test() to let me do this test again.