We're supposed to call if our kids are going to be out, but we don't have to bring a doctor's note. We're supposed to send a note in when they go back to school, but it can be a parent's note. If I do take them to the doctor or dentist I ask for a note, but otherwise I don't make a special trip to the doctor just to get a note. My kids aren't sick very often and we don't go to the doctor very often either.
I just read an article on HuffPo about opting out of testing in PA. I'm in NC and from my reading of the rules, I don't think we're allowed to opt out for any reason. Private schools can opt out, but all public school, charter school, and homeschool kids are required to test. I'm sure we could reschedule for illness, but I think they are required to take it, at least for certain years.