tests/arrpc: add service module test coverage

- Add custom-target.nix test for custom systemd target configuration

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

tests/modules/services/arrpc/custom-target-expected.service

@@ -0,0 +1,10 @@
+[Install]
+WantedBy=sway-session.target
+
+[Service]
+ExecStart=@arrpc@/bin/arrpc
+Restart=always
+
+[Unit]
+Description=Discord Rich Presence for browsers, and some custom clients
+PartOf=graphical-session.target

tests/modules/services/arrpc/custom-target.nix

@@ -0,0 +1,14 @@
+{
+  config = {
+    services.arrpc = {
+      enable = true;
+      systemdTarget = "sway-session.target";
+    };
+
+    nmt.script = ''
+      assertFileContent \
+        home-files/.config/systemd/user/arRPC.service \
+        ${./custom-target-expected.service}
+    '';
+  };
+}

tests/modules/services/arrpc/default.nix

@@ -0,0 +1,4 @@
+{ lib, pkgs, ... }:
+lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
+  arrpc-custom-target = ./custom-target.nix;
+}