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

modules/serviceTests/stub.nix

@@ -0,0 +1,20 @@
+/**
+  Module to make writing service-specific tests easy.
+*/
+{ lib, ... }:
+let
+  inherit (lib) mkOption types;
+in
+{
+  options = {
+    serviceTests = mkOption {
+      type = types.attrsOf types.package;
+
+      description = ''
+        NixOS tests to run.
+      '';
+
+      default = { };
+    };
+  };
+}