commit https://github.com/vim/vim/commit/04c4ce650f9e533cd35b2aa6803f4d354d3ec7aa Author: Bram Moolenaar <Bram@vim.org> Date: Thu Sep 1 15:45:58 2016 +0200 patch 7.4.2299 Problem: QuickFixCmdPre and QuickFixCmdPost autocommands are not always triggered. Solution: Also trigger on ":expr", ":cbuffer", etc. (Yegappan Lakshmanan)

" Test for joining lines.

func Test_join_with_count()
  new
  call setline(1, ['one', 'two', 'three', 'four'])
  normal J
  call assert_equal('one two', getline(1))
  %del
  call setline(1, ['one', 'two', 'three', 'four'])
  normal 10J
  call assert_equal('one two three four', getline(1))
  quit!
endfunc