diff --git a/cluster/lib/service-module.nix b/cluster/lib/service-module.nix
index 9cdc5ee..bd69f41 100644
--- a/cluster/lib/service-module.nix
+++ b/cluster/lib/service-module.nix
@@ -57,10 +57,17 @@ in
       deps = mkOption {
         description = "Other services to include.";
         type = with types; listOf str;
+        default = [];
       };
       settings = mkOption {
-        description = "Additional NixOS test configuration.";
+        description = "NixOS test configuration.";
         type = types.deferredModule;
+        default.testScript = lib.mkDefault "assert False";
+      };
+      augments = mkOption {
+        description = "Cluster augments (will be propagated).";
+        type = types.deferredModule;
+        default = {};
       };
     };
   };
diff --git a/cluster/lib/testing.nix b/cluster/lib/testing.nix
new file mode 100644
index 0000000..6c96b37
--- /dev/null
+++ b/cluster/lib/testing.nix
@@ -0,0 +1,9 @@
+{ lib, ... }:
+
+{
+  options.simulacrum = lib.mkOption {
+    description = "Whether we are in the Simulacrum.";
+    type = lib.types.bool;
+    default = false;
+  };
+}