tests/caffeine: add test coverage

- Add basic-service.nix test for caffeine service configuration
- Test systemd service generation with proper graphical-session.target
integration

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

tests/modules/services/caffeine/basic-service-expected.service

@@ -0,0 +1,13 @@
+[Install]
+WantedBy=graphical-session.target
+
+[Service]
+ExecStart=@caffeine-ng@/bin/caffeine
+PrivateTmp=true
+ProtectSystem=full
+Restart=on-failure
+Slice=session.slice
+Type=exec
+
+[Unit]
+Description=caffeine

tests/modules/services/caffeine/basic-service.nix

@@ -0,0 +1,15 @@
+{ config, ... }:
+
+{
+  config = {
+    services.caffeine = {
+      enable = true;
+    };
+
+    nmt.script = ''
+      assertFileContent \
+        home-files/.config/systemd/user/caffeine.service \
+        ${./basic-service-expected.service}
+    '';
+  };
+}

tests/modules/services/caffeine/default.nix

@@ -0,0 +1,5 @@
+{ lib, pkgs, ... }:
+
+lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
+  caffeine-basic-service = ./basic-service.nix;
+}