test(nginx): Add simple tests to assert nginx features work

configuration/nginx/logging.nix

@@ -1,4 +1,10 @@
-{ config, lib, ... }:
+{
+  flake-inputs,
+  pkgs,
+  config,
+  lib,
+  ...
+}:
 let
   hostNames = lib.attrNames config.services.nginx.virtualHosts;
   logPath = name: "/var/log/nginx/${name}/access.log";
@@ -80,5 +86,55 @@ in
         };
       };
     };
+
+    serviceTests =
+      let
+        testHostConfig =
+          { config, ... }:
+          {
+            imports = [
+              ./.
+              ../../modules/serviceTests/mocks.nix
+            ];
+
+            networking.firewall.allowedTCPPorts = [ 80 ];
+
+            services.nginx = {
+              domain = "testHost";
+              virtualHosts."${config.services.nginx.domain}".locations."/".return = "200 ok";
+            };
+          };
+      in
+      {
+        nginxMetricsWork = pkgs.testers.runNixOSTest {
+          name = "nginx-metrics-work";
+          node.specialArgs = { inherit flake-inputs; };
+
+          nodes = {
+            testHost = testHostConfig;
+
+            client =
+              { pkgs, ... }:
+              {
+                environment.systemPackages = [ pkgs.curl ];
+              };
+          };
+
+          testScript = ''
+            import time
+
+            start_all()
+
+            testHost.wait_for_unit("nginx.service")
+            client.succeed("curl --max-time 10 http://testHost")
+
+            # Wait a bit for the prometheus exporter to scrape our logs
+            time.sleep(5)
+
+            res = testHost.succeed("curl localhost:${builtins.toString config.services.prometheus.exporters.nginxlog.port}/metrics")
+            assert 'nginxlog_http_response_count_total{method="GET",status="200",vhost="testHost"} 1' in res, res
+          '';
+        };
+      };
   };
 }