commit https://github.com/vim/vim/commit/6244a0fc29163ba1c734f92b55a89e01e6cf2a67 Author: Bram Moolenaar <Bram@vim.org> Date: Thu Apr 14 14:09:25 2016 +0200 patch 7.4.1729 Problem: The Perl interface cannot use 'print' operator for writing directly in standard IO. Solution: Add a minimal implementation of PerlIO Layer feature and try to use it for STDOUT/STDERR. (Damien)

" 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('.'))

  " check it goes back to normal mode immediately.
  call feedkeys('i', 'x')
  call assert_equal('foo', getline('.'))
  quit!
endfunc