installers/tools: add test for system.disableInstallerTools option

This test ensures the installer tools are actually unavailable
with the option set to true.

nixos/tests/all-tests.nix

@@ -98,6 +98,7 @@ in
   deluge = handleTest ./deluge.nix {};
   dendrite = handleTest ./dendrite.nix {};
   dhparams = handleTest ./dhparams.nix {};
+  disable-installer-tools = handleTest ./disable-installer-tools.nix {};
   discourse = handleTest ./discourse.nix {};
   dnscrypt-proxy2 = handleTestOn ["x86_64-linux"] ./dnscrypt-proxy2.nix {};
   dnscrypt-wrapper = handleTestOn ["x86_64-linux"] ./dnscrypt-wrapper {};

nixos/tests/disable-installer-tools.nix

@@ -0,0 +1,29 @@
+import ./make-test-python.nix ({ pkgs, latestKernel ? false, ... }:
+
+{
+  name = "disable-installer-tools";
+
+  machine =
+    { pkgs, lib, ... }:
+    {
+        system.disableInstallerTools = true;
+        boot.enableContainers = false;
+        environment.defaultPackages = [];
+    };
+
+  testScript = ''
+      machine.wait_for_unit("multi-user.target")
+      machine.wait_until_succeeds("pgrep -f 'agetty.*tty1'")
+
+      with subtest("nixos installer tools should not be included"):
+          machine.fail("which nixos-rebuild")
+          machine.fail("which nixos-install")
+          machine.fail("which nixos-generate-config")
+          machine.fail("which nixos-enter")
+          machine.fail("which nixos-version")
+          machine.fail("which nixos-build-vms")
+
+      with subtest("perl should not be included"):
+          machine.fail("which perl")
+  '';
+})