nixos/vnstat: add NixOS test

nixos/tests/all-tests.nix

@@ -1844,6 +1844,7 @@ in
   };
   virtualbox = handleTestOn [ "x86_64-linux" ] ./virtualbox.nix { };
   vm-variant = handleTest ./vm-variant.nix { };
+  vnstat = runTest ./vnstat.nix;
   vscode-remote-ssh = handleTestOn [ "x86_64-linux" ] ./vscode-remote-ssh.nix { };
   vscodium = import ./vscodium.nix { inherit runTest; };
   vsftpd = runTest ./vsftpd.nix;

nixos/tests/vnstat.nix

@@ -0,0 +1,26 @@
+{ lib, ... }:
+{
+  name = "vnstat";
+  meta.maintainers = with lib.maintainers; [ hmenke ];
+
+  containers.machine = {
+    services.vnstat = {
+      enable = true;
+      settings = {
+        AlwaysAddNewInterfaces = 1;
+      };
+    };
+  };
+
+  testScript = ''
+    start_all()
+
+    machine.wait_for_unit("vnstat.service")
+
+    machine.succeed("vnstat --iflist")
+    machine.fail("vnstat -i dummy0")
+    machine.succeed("ip link add dummy0 type dummy")
+    machine.succeed("ip link set dummy0 up")
+    machine.wait_until_succeeds("vnstat -i dummy0", timeout=10)
+  '';
+}

pkgs/by-name/vn/vnstat/package.nix

@@ -7,6 +7,7 @@
   ncurses,
   sqlite,
   check,
+  nixosTests,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -40,6 +41,8 @@ stdenv.mkDerivation (finalAttrs: {
 
   doCheck = true;
 
+  passthru.tests = { inherit (nixosTests) vnstat; };
+
   meta = {
     description = "Console-based network statistics utility for Linux";
     longDescription = ''