Fix error handling and add nixos test

flake.nix

@@ -2,7 +2,7 @@
   description = "a653rs-router";
 
   inputs = {
-   flake-utils.url = "github:numtide/flake-utils";
+    flake-utils.url = "github:numtide/flake-utils";
   };
 
   outputs =
@@ -16,9 +16,9 @@
       let
         pkgs = import nixpkgs { inherit system; };
       in
-      {
+      rec {
         devShells.default = pkgs.mkShell {
-         nativeBuildInputs = [
+          nativeBuildInputs = [
             pkgs.cargo
             pkgs.clang
             pkgs.clippy
@@ -31,10 +31,25 @@
           ];
         };
         packages = {
-          default = pkgs.callPackage ./default.nix {};
+          default = pkgs.callPackage ./default.nix { };
+        };
+        checks = {
+          vm = nixpkgs.lib.nixos.runTest (
+            import ./test.nix {
+              pkgs = import nixpkgs {
+                inherit system;
+                overlays = [
+                  (final: prev: {
+                    pam_honeypot = packages.default;
+                  })
+                ];
+              };
+            }
+          );
         };
       }
-    ) // {
+    )
+    // {
       nixosModules = {
         default = ./module.nix;
       };