commit https://github.com/vim/vim/commit/e59215c7dcae17b03daf39517560cfaa03314f5a Author: Bram Moolenaar <Bram@vim.org> Date: Sun Aug 14 19:08:45 2016 +0200 patch 7.4.2212 Problem: Mark " is not set when closing a window in another tab. (Guraga) Solution: Check all tabs for the window to be valid. (based on patch by Hirohito Higashi, closes https://github.com/vim/vim/issues/974)

start:
test for empty string: ok
test for 1 char: ok
test for 3 chars: ok
test for contains meta char: ok
test for contains non-ascii char: ok