commit https://github.com/vim/vim/commit/d29459baa61819e59961804ed258efac5733ec70 Author: Bram Moolenaar <Bram@vim.org> Date: Fri Aug 26 22:29:11 2016 +0200 patch 7.4.2263 Problem: :filter does not work for many commands. Can only get matching messages. Solution: Make :filter work for :command, :map, :list, :number and :print. Make ":filter!" show non-matching lines.

" 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