Bathroom door is closed. Do you knock?

I don't, because when I'm in the bathroom and hear a knock, for some reason there's always a moment of panic that they'll barge in. And then you have to awkwardly be like "Um...yes?" or "Someone's here!"

what do you even say? Just quietly jiggle the handle, no interaction with the person in the bathroom necessary.

Needs an option for both

I knock whilst jiggling the handle to see if it's locked, but I don't push the door open (if unlocked) for a few seconds of silence. I sometimes crack it to hear a little better without looking in.

Cracking the door also lets you see if the light is on or off. If it's off then easy.

Depends if the light is on

I just kick the door down, deed in hand

Nope. I generally know where Mrs. DevsBro is at all times.