diff --git a/flake.lock b/flake.lock
index bcef6ac..4eb0d97 100644
--- a/flake.lock
+++ b/flake.lock
@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1611784459,
-        "narHash": "sha256-f5ZAW9dK/m2W2F+Gsb9nVuGTcVbnhkUezfaqWYaXAF8=",
+        "lastModified": 1611948132,
+        "narHash": "sha256-mH7hD1ps1FcRaVdP36jZWZFHdESVPY5rdTNJR16z7D4=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "5547b2f67042994ec0155cef24296681dc7fba5a",
+        "rev": "aa48e205a2e0516ff4b96c79eeb666aaaccd418c",
         "type": "github"
       },
       "original": {
diff --git a/flake.nix b/flake.nix
index bcdd768..122e467 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,25 +1,27 @@
 {
   description = "Genode packages";
 
-
   outputs = { self, nixpkgs }:
     let
-      localSystems = [ "x86_64-linux" ];
-      crossSystems = [ "aarch64-genode" "x86_64-genode" ];
+      systems = {
+        localSystem = [ "x86_64-linux" ];
+        crossSystem = [ "aarch64-genode" "x86_64-genode" ];
+      };
+      systemSpace = nixpkgs.lib.cartesianProductOfSets systems;
 
       forAllLocalSystems = f:
-        nixpkgs.lib.genAttrs localSystems (system: f system);
+        nixpkgs.lib.genAttrs systems.localSystem (system: f system);
 
       forAllCrossSystems = f:
         with builtins;
         let
-          f' = localSystem: crossSystem:
+          f' = { localSystem, crossSystem }:
             let system = localSystem + "-" + crossSystem;
             in {
               name = system;
               value = f { inherit system localSystem crossSystem; };
             };
-          list = nixpkgs.lib.lists.crossLists f' [ localSystems crossSystems ];
+          list = map f' systemSpace;
           attrSet = listToAttrs list;
         in attrSet;
 
diff --git a/tests/default.nix b/tests/default.nix
index 8a76c86..29cca13 100644
--- a/tests/default.nix
+++ b/tests/default.nix
@@ -7,59 +7,59 @@ let
 
   testingPython = import ./lib/testing-python.nix;
 
-  testSpecs = map (p: import p) [
-    ./ahci.nix
-    ./bash.nix
-    ./hello.nix
-    ./log.nix
-    ./vmm_x86.nix
-    ./x86.nix
-  ];
+  testSpace = lib.cartesianProductOfSets {
 
-  cores = [
-    /* {
-         prefix = "hw-pc-";
-         testingPython = testingPython {
-           inherit flake system localSystem crossSystem pkgs;
-           extraConfigurations = [ ../nixos-modules/base-hw-pc.nix ];
-         };
-         specs = [ "x86" "hw" ];
-         platforms = [ "x86_64-genode" ];
-       }
-    */
-    /* {
-         prefix = "hw-virt_qemu-";
-         testingPython = testingPython {
-           inherit flake system localSystem crossSystem pkgs;
-           extraConfigurations = [ ../nixos-modules/base-hw-virt_qemu.nix ];
-         };
-         specs = [ "aarch64" "hw" ];
-         platforms = [ "aarch64-genode" ];
-       }
-    */
-    {
-      prefix = "nova-";
-      testingPython = testingPython {
-        inherit flake system localSystem crossSystem pkgs;
-        extraConfigurations = [ ../nixos-modules/nova.nix ];
-      };
-      specs = [ "x86" "nova" ];
-      platforms = [ "x86_64-genode" ];
-    }
-  ];
+    test = map (p: import p) [
+      ./ahci.nix
+      ./bash.nix
+      ./hello.nix
+      ./log.nix
+      ./vmm_x86.nix
+      ./x86.nix
+    ];
 
-  cores' = builtins.filter (core:
-    builtins.any (x: x == pkgs.stdenv.hostPlatform.system) core.platforms)
-    cores;
+    core = builtins.filter (core:
+      builtins.any (x: x == pkgs.stdenv.hostPlatform.system) core.platforms) [
+        /* {
+             prefix = "hw-pc-";
+             testingPython = testingPython {
+               inherit flake system localSystem crossSystem pkgs;
+               extraConfigurations = [ ../nixos-modules/base-hw-pc.nix ];
+             };
+             specs = [ "x86" "hw" ];
+             platforms = [ "x86_64-genode" ];
+           }
+        */
+        /* {
+             prefix = "hw-virt_qemu-";
+             testingPython = testingPython {
+               inherit flake system localSystem crossSystem pkgs;
+               extraConfigurations = [ ../nixos-modules/base-hw-virt_qemu.nix ];
+             };
+             specs = [ "aarch64" "hw" ];
+             platforms = [ "aarch64-genode" ];
+           }
+        */
+        {
+          prefix = "nova-";
+          testingPython = testingPython {
+            inherit flake system localSystem crossSystem pkgs;
+            extraConfigurations = [ ../nixos-modules/nova.nix ];
+          };
+          specs = [ "x86" "nova" ];
+          platforms = [ "x86_64-genode" ];
+        }
+      ];
+
+  };
 
   testList = let
-    f = core: test:
+    f = { core, test }:
       if (test.constraints or (_: true)) core.specs then {
         name = core.prefix + test.name;
         value = core.testingPython.makeTest test;
       } else
         null;
-
-  in lib.lists.crossLists f [ cores' testSpecs ];
+  in map f testSpace;
 
 in builtins.listToAttrs (builtins.filter (_: _ != null) testList)