1 files changed, 36 insertions, 0 deletions
diff --git a/nixpkgs/nixos/tests/activation/etc-overlay-immutable.nix b/nixpkgs/nixos/tests/activation/etc-overlay-immutable.nix
new file mode 100644
index 000000000000..f347f9cf8efe
--- /dev/null
+++ b/nixpkgs/nixos/tests/activation/etc-overlay-immutable.nix
@@ -0,0 +1,36 @@
+{ lib, ... }: {
+
+  name = "activation-etc-overlay-immutable";
+
+  meta.maintainers = with lib.maintainers; [ nikstur ];
+
+  nodes.machine = { pkgs, ... }: {
+    system.etc.overlay.enable = true;
+    system.etc.overlay.mutable = false;
+
+    # Prerequisites
+    systemd.sysusers.enable = true;
+    users.mutableUsers = false;
+    boot.initrd.systemd.enable = true;
+    boot.kernelPackages = pkgs.linuxPackages_latest;
+
+    specialisation.new-generation.configuration = {
+      environment.etc."newgen".text = "newgen";
+    };
+  };
+
+  testScript = ''
+    with subtest("/etc is mounted as an overlay"):
+      machine.succeed("findmnt --kernel --type overlay /etc")
+
+    with subtest("switching to the same generation"):
+      machine.succeed("/run/current-system/bin/switch-to-configuration test")
+
+    with subtest("switching to a new generation"):
+      machine.fail("stat /etc/newgen")
+
+      machine.succeed("/run/current-system/specialisation/new-generation/bin/switch-to-configuration switch")
+
+      assert machine.succeed("cat /etc/newgen") == "newgen"
+  '';
+}