commit https://github.com/vim/vim/commit/89b10421ca1aea55acbafac1df93be4e20210ceb Author: Bram Moolenaar <Bram@vim.org> Date: Tue Jul 12 22:51:22 2016 +0200 patch 7.4.2031 Problem: The list_lbr_utf8 test fails if ~/.vim/syntax/c.vim sets 'textwidth' to a non-zero value. (Oyvind A. Holm) Solution: Add a setup.vim file that sets 'runtimepath' and $HOME to a safe value. (partly by Christian Brabandt, closes #912)

" Common preparations for running tests.

" Make sure 'runtimepath' does not include $HOME.
set rtp=$VIM/vimfiles,$VIMRUNTIME,$VIM/vimfiles/after

" Only when the +eval feature is present. 
if 1
  " Make sure $HOME does not get read or written.
  let $HOME = '/does/not/exist'
endif