too lazy to think of a message, so enjoy this pointless text. Good luck future me...

checks/customer-portal/default.nix

@@ -0,0 +1,22 @@
+{
+  pkgs,
+  nixosLib,
+  clan-core,
+  ...
+}:
+nixosLib.runTest (
+  { ... }:
+  {
+    imports = [
+      clan-core.modules.nixosTest.clanTest
+    ];
+
+    hostPkgs = pkgs;
+
+    name = "service-customer-portal";
+
+    testScript = ''
+      start_all()
+    '';
+  }
+)

checks/flake-module.nix

@@ -0,0 +1,15 @@
+{ self, ... }:
+let
+  nixosLib = import (self.inputs.nixpkgs + "/nixos/lib") { };
+in
+{
+  perSystem = { pkgs, lib, ... }:
+  {
+    checks = {
+      service-customer-portal-test = import ./customer-portal {
+        inherit pkgs lib nixosLib self;
+        inherit (self.inputs) clan-core;
+      };
+    };
+  };
+}

clanServices/customer-portal/default.nix

@@ -1,4 +1,4 @@
-{ ... }:
+{ self, ... }:
 let
   inherit (builtins) readFile;
 in
@@ -26,6 +26,8 @@ in
 
     perInstance = { instanceName, settings, machine, roles, ... }: {
       nixosModule = { config, pkgs, ... }: {
+        imports = [ self.inputs.amarth-customer-portal.nixosModules.default ];
+
         services.amarth-customer-portal = {
           enable = true;
         };

clanServices/customer-portal/flake-module.nix

@@ -1,13 +1,15 @@
-{ ... }:
+{ self, lib, ... }:
 let
-  module = ./default.nix;
+  module = lib.modules.importApply ./default.nix { inherit self; };
 in
 {
   clan.modules.customer-portal = module;
 
   perSystem = { ... }: {
     clan.nixosTests.customer-portal = {
-      imports = [ ./tests/vm/default.nix ];
+      imports = [
+        ./tests/vm/default.nix
+      ];
 
       clan.modules."@amarth/customer-portal" = module;
     };

devShells/flake-module.nix

@@ -4,6 +4,7 @@
       packages = with pkgs; [
         bash
         sops
+        just
 
         inputs'.clan-core.packages.clan-cli
       ];

flake.nix

@@ -34,6 +34,7 @@
         clan-core.flakeModules.default
         clan-core.flakeModules.testModule
 
+        # ./checks/flake-module.nix
         ./devShells/flake-module.nix
         ./clanServices/flake-module.nix
       ];