how do they test to see if water has a small tear?

Jolene • Momma of a beautiful girl Kinsley Anne born Jan 18th 2016 and due with our 2nd girl Maddison Reece due May 15th 2017
For those mommas who have gone to the hospital thinking they have a leak in their waters. I know they do a swab but do they do a swab in your vagina or like a pad you bring to them? 
Just curious. Last night before I went pee I went to wipe because I felt wet just wanted to check and right when I went to wipe I had a tiny tiny trickle down my leg I smelled it didn't smell like anything and was clear, I swayed and walked around the house, and layed down for a little and got back up and nothing else happened so I just dismissed it as my bladder. And I haven't had very much discharge at all, like I don't have to wear a panty liner and I can wear the same undies all day and it will only be slightly dirty by the end of the day, but I do notice wet spot(that dried)around with a clearish whiteish tad watery discharge. 
I'm 5 days away from due date so u know how it is looking for any signs that labor is here I don't want to over think it or go in when it is nothing just normal stuff(because hospital is an hr away) 
But I almost wounder if i do have a slow leak, my stomach hasn't grown since 38 wks (I was measuring ahead) and it's like my measurements slowed down and now stopped, could be other things than my water. But I haven't had an ultrasound since 19 wks. 
And another question is if it's your water when u pee in a cup and they test for protein is that what's in your waters? Like what exactly is that they are testing??