xsession: verify setxkbmap service in test

tests/modules/misc/xsession/basic-setxkbmap-expected.service

@@ -0,0 +1,12 @@
+[Install]
+WantedBy=graphical-session.target
+
+[Service]
+ExecStart=@setxkbmap@/bin/setxkbmap -layout 'us' -variant ''
+RemainAfterExit=true
+Type=oneshot
+
+[Unit]
+After=graphical-session-pre.target
+Description=Set up keyboard in X
+PartOf=graphical-session.target

tests/modules/misc/xsession/basic.nix

@@ -1,4 +1,4 @@
-{ config, lib, ... }:
+{ config, lib, pkgs, ... }:
 
 with lib;
 
@@ -25,6 +25,13 @@ with lib;
         home-files/.xsession \
         ${./basic-xsession-expected.txt}
 
+      assertFileExists home-files/.config/systemd/user/setxkbmap.service
+      assertFileContent \
+        home-files/.config/systemd/user/setxkbmap.service \
+        ${pkgs.substituteAll {
+          src = ./basic-setxkbmap-expected.service;
+          inherit (pkgs.xorg) setxkbmap;
+        }}
     '';
   };
 }