commit https://github.com/vim/vim/commit/b681be175b6991cdc2b8ddd49b0e97e3fe2b201e Author: Bram Moolenaar <Bram@vim.org> Date: Thu Mar 31 23:02:16 2016 +0200 patch 7.4.1691 Problem: When switching to a new buffer and an autocommand applies syntax highlighting an ml_get error may occur. Solution: Check "syn_buf" against the buffer in the window. (Alexander von Buddenbrock, closes #676)

" Tests for :undo

func Test_ex_undo()
  new ex-undo
  setlocal ul=10
  exe "normal ione\n\<Esc>"
  setlocal ul=10
  exe "normal itwo\n\<Esc>"
  setlocal ul=10
  exe "normal ithree\n\<Esc>"
  call assert_equal(4, line('$'))
  undo
  call assert_equal(3, line('$'))
  undo 1
  call assert_equal(2, line('$'))
  undo 0
  call assert_equal(1, line('$'))
  quit!
endfunc