anchor.diff:  
     checkPhase = stdenv.lib.optionalString (stdenv.system == "x86_64-linux")
     ''
  -    ln -sf "${xdummy}/bin/xdummy" testcases/Xdummy
  -    (cd testcases && perl complete-run.pl -p 1)
  +    (cd testcases && xvfb-run ./complete-run.pl -p 1)
       ! grep -q '^not ok' testcases/latest/complete-run.log
     '';
   
  
positive.code: { fetchurl, stdenv, which, pkgconfig, makeWrapper, libxcb, xcbutilkeysyms
  , xcbutil, xcbutilwm, libstartup_notification, libX11, pcre, libev, yajl
  , xcb-util-cursor, coreutils, perl, pango, perlPackages, xdummy, libxkbcommon }:
  
  stdenv.mkDerivation rec {
    name = "i3-${version}";
    version = "4.9.1";
  
    src = fetchurl {
      url = "http://i3wm.org/downloads/${name}.tar.bz2";
      sha256 = "0hyw2rdxigiklqvv7fbhcdqdxkgcxvx56vk4r5v55l674zqfy3dp";
    };
  
    buildInputs = [
  
negative.code:     libstartup_notification libX11 pcre libev yajl xcb-util-cursor perl pango
      perlPackages.AnyEventI3 perlPackages.X11XCB perlPackages.IPCRun
      perlPackages.ExtUtilsPkgConfig perlPackages.TestMore perlPackages.InlineC
      xorgserver xvfb_run
    ];
  
    postPatch = ''
  