nixosTests.scanservjs: init

Test that the service runs and uses our configured (TCP) port.

This should prevent https://github.com/NixOS/nixpkgs/issues/475043
("nixos/scanservjs: settings (host/port) ignored in v3.0.4") from
happening again.

nixos/tests/all-tests.nix

@@ -1489,6 +1489,7 @@ in
   sane = runTest ./sane.nix;
   sanoid = runTest ./sanoid.nix;
   saunafs = runTest ./saunafs.nix;
+  scanservjs = runTest ./scanservjs.nix;
   scaphandre = runTest ./scaphandre.nix;
   schleuder = runTest ./schleuder.nix;
   scion-freestanding-deployment = runTest ./scion/freestanding-deployment;

nixos/tests/scanservjs.nix

@@ -0,0 +1,23 @@
+let
+  port = 1234;
+in
+{
+  name = "scanservjs";
+
+  nodes.machine =
+    { ... }:
+    {
+      services.scanservjs = {
+        enable = true;
+        settings.host = "0.0.0.0";
+        settings.port = port;
+      };
+    };
+
+  testScript = ''
+    machine.wait_for_unit("scanservjs.service")
+    machine.wait_until_succeeds(
+        "curl --silent --fail --show-error --location http://localhost:${toString port}"
+    )
+  '';
+}