commit https://github.com/vim/vim/commit/9532fe7fbe1b14531931e83bd9f8054efdcf7509 Author: Bram Moolenaar <Bram@vim.org> Date: Fri Jul 29 22:50:35 2016 +0200 patch 7.4.2121 Problem: No easy way to check if lambda and closure are supported. Solution: Add the +lambda feature.

" 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