commit https://github.com/vim/vim/commit/8b877ac38e96424a08a8b8eb713ef4b3cf0064be Author: Bram Moolenaar <Bram@vim.org> Date: Mon Mar 28 19:16:20 2016 +0200 patch 7.4.1669 Problem: When writing buffer lines to a pipe Vim may block. Solution: Avoid blocking, write more lines later.

" Test feedkeys() function.

func Test_feedkeys_x_with_empty_string()
  new
  call feedkeys("ifoo\<Esc>")
  call assert_equal('', getline('.'))
  call feedkeys('', 'x')
  call assert_equal('foo', getline('.'))
  quit!
endfunc