swayosd: add module

tests/modules/services/swayosd/default.nix

@@ -0,0 +1 @@
+{ swayosd = ./swayosd.nix; }

tests/modules/services/swayosd/swayosd.nix

@@ -0,0 +1,35 @@
+{ config, ... }:
+
+{
+  services.swayosd = {
+    enable = true;
+    package = config.lib.test.mkStubPackage {
+      name = "swayosd";
+      outPath = "@swayosd@";
+    };
+    maxVolume = 10;
+  };
+
+  nmt.script = ''
+    assertFileContent \
+      home-files/.config/systemd/user/swayosd.service \
+      ${
+        builtins.toFile "swayosd.service" ''
+          [Install]
+          WantedBy=graphical-session.target
+
+          [Service]
+          ExecStart=@swayosd@/bin/swayosd --max-volume 10
+          Restart=always
+          Type=simple
+
+          [Unit]
+          After=graphical-session.target
+          ConditionEnvironment=WAYLAND_DISPLAY
+          Description=Volume/backlight OSD indicator
+          Documentation=man:swayosd(1)
+          PartOf=graphical-session.target
+        ''
+      }
+  '';
+}