patch 8.1.1362: code and data in tests can be hard to read commit https://github.com/vim/vim/commit/c79745a82faeb5a6058e915ca49a4c69fa60ea01 Author: Bram Moolenaar <Bram@vim.org> Date: Mon May 20 22:12:34 2019 +0200 patch 8.1.1362: code and data in tests can be hard to read Problem: Code and data in tests can be hard to read. Solution: Use the new heredoc style. (Yegappan Lakshmanan, closes https://github.com/vim/vim/issues/4400)

" Simplistic way to make spaces and Tabs visible

" This can be added to an already active syntax.

syn match Space " "
syn match Tab "\t"
if &background == "dark"
  hi def Space ctermbg=darkred guibg=#500000
  hi def Tab ctermbg=darkgreen guibg=#003000
else
  hi def Space ctermbg=lightred guibg=#ffd0d0
  hi def Tab ctermbg=lightgreen guibg=#d0ffd0
endif