make system-to-install re-usuable for other tests

this is needed for the ubuntu test.

Author: Mic92

tests/flake-module.nix

@@ -3,11 +3,16 @@
 {
   flake.checks.x86_64-linux = withSystem "x86_64-linux" ({ pkgs, system, inputs', config, ... }:
     let
+      system-to-install = pkgs.nixos [
+        ./modules/system-to-install.nix
+        inputs.disko.nixosModules.disko
+      ];
       testInputsUnstable = {
         inherit pkgs;
         inherit (inputs.disko.nixosModules) disko;
         nixos-anywhere = config.packages.nixos-anywhere;
         kexec-installer = "${inputs'.nixos-images.packages.kexec-installer-nixos-unstable-noninteractive}/nixos-kexec-installer-noninteractive-${system}.tar.gz";
+        inherit system-to-install;
       };
       testInputsStable = testInputsUnstable // {
         kexec-installer = "${inputs'.nixos-images.packages.kexec-installer-nixos-stable-noninteractive}/nixos-kexec-installer-noninteractive-${system}.tar.gz";

tests/lib/test-base.nix

@@ -1,8 +1,9 @@
 test:
-{ pkgs ? import <nixpkgs> { }
-, nixos-anywhere ? pkgs.callPackage ../../src { }
-, disko ? "${builtins.fetchTarball "https://github.com/nix-community/disko/archive/master.tar.gz"}/module.nix"
-, kexec-installer ? builtins.fetchurl "https://github.com/nix-community/nixos-images/releases/download/nixos-unstable/nixos-kexec-installer-noninteractive-${pkgs.stdenv.hostPlatform.system}.tar.gz"
+{ pkgs
+, nixos-anywhere
+, disko
+, kexec-installer
+, system-to-install
 , ...
 }:
 let
@@ -14,6 +15,6 @@ in
   # speed-up evaluation
   defaults.documentation.enable = lib.mkDefault false;
   # to accept external dependencies such as disko
-  node.specialArgs.inputs = { inherit nixos-anywhere disko kexec-installer; };
+  node.specialArgs.inputs = { inherit nixos-anywhere disko kexec-installer system-to-install; };
   imports = [ test ];
 }).config.result

tests/modules/installer.nix

@@ -1,12 +1,4 @@
 { pkgs, inputs, ... }:
-let
-  disko = inputs.disko;
-  kexec-installer = inputs.kexec-installer;
-  system-to-install = pkgs.nixos [
-    ./system-to-install.nix
-    disko
-  ];
-in
 {
   system.activationScripts.rsa-key = ''
     ${pkgs.coreutils}/bin/install -D -m600 ${./ssh-keys/ssh} /root/.ssh/install_key
@@ -15,8 +7,8 @@ in
   environment.systemPackages = [ inputs.nixos-anywhere ];
 
   environment.etc = {
-    "nixos-anywhere/disko".source = system-to-install.config.system.build.diskoScriptNoDeps;
-    "nixos-anywhere/system-to-install".source = system-to-install.config.system.build.toplevel;
-    "nixos-anywhere/kexec-installer".source = kexec-installer;
+    "nixos-anywhere/disko".source = inputs.system-to-install.config.system.build.diskoScriptNoDeps;
+    "nixos-anywhere/system-to-install".source = inputs.system-to-install.config.system.build.toplevel;
+    "nixos-anywhere/kexec-installer".source = inputs.kexec-installer;
   };
 }