I didn't sit any test other than the TOEIC for my engineering school (scored 980) and that covers only reading and listening.
I feel like I achieved most of my "mastery" (not to say that I know everything, far from it) in English with the 3 points I listed before and didn't improve much by living in an English speaking country. Which I still loved, living in an English country, that is.
I lived in Australia, Melbourne in particular for about one year and worked in the IT department of a call center there. I really wanted to work in my field (computer science) in an English speaking country to really have an in-depth experience and it was a personal success (I loved it), but didn't change must regarding my English skills. I think I had reached a level of English on my own that made it so that living in an English country didn't improve it more. However, I feel like (and heard that) that experience would be a really good kick-start for someone still below on the learning curve.
It ok
Harry Potter fanfictions to quench my HP universe thirst that the books left me with.