actually including nixos-facter + nixos test

nix/installer.nix

@@ -34,7 +34,7 @@
     # for copying extra files of nixos-anywhere
     pkgs.rsync
     # alternative to nixos-generate-config
-  ] ++ lib.optional (pkgs.lib.versionAtLeast lib.version "24.11") pkgs.nixos-facter;
+  ] ++ lib.optional (pkgs ? nixos-facter) pkgs.nixos-facter;
 
   # Don't add nixpkgs to the image to save space, for our intended use case we don't need it
   system.installer.channel.enable = false;

nix/kexec-installer/test.nix

@@ -1,6 +1,7 @@
 { pkgs
 , lib
 , kexecTarball
+, nixos-facter ? null
 }:
 
 pkgs.testers.runNixOSTest {
@@ -69,6 +70,7 @@ pkgs.testers.runNixOSTest {
   };
 
   testScript = /*python*/ ''
+    import json
     import time
     import subprocess
     import socket
@@ -163,6 +165,11 @@ pkgs.testers.runNixOSTest {
     host = ssh(["hostname"], stdout=subprocess.PIPE).stdout.strip()
     assert host == "nixos-installer", f"hostname is {host}, not nixos-installer"
 
+    has_nixos_facter=${if nixos-facter != null then "True" else "False"}
+    if has_nixos_facter == True:
+        data = json.loads(ssh(["nixos-facter"], stdout=subprocess.PIPE).stdout)
+        assert data["virtualisation"] == "kvm", f"virtualisation is {data['virtualisation']}, not kvm"
+
     host_ed25519_after = ssh(["cat", "/etc/ssh/ssh_host_ed25519_key.pub"], stdout=subprocess.PIPE).stdout.strip()
     assert host_ed25519_before == host_ed25519_after, f"'{host_ed25519_before}' != '{host_ed25519_after}'"