adding nixosModule and test

test/lib.nix

@@ -0,0 +1,21 @@
+# tests/lib.nix
+# based on https://blog.thalheim.io/2023/01/08/how-to-use-nixos-testing-framework-with-flakes/
+# The first argument to this function is the test module itself
+test:
+# These arguments are provided by `flake.nix` on import, see checkArgs
+{ pkgs, self}:
+let
+  inherit (pkgs) lib;
+  # this imports the nixos library that contains our testing framework
+  nixos-lib = import (pkgs.path + "/nixos/lib") {};
+in
+(nixos-lib.runTest {
+  hostPkgs = pkgs;
+  # This speeds up the evaluation by skipping evaluating documentation (optional)
+  defaults.documentation.enable = lib.mkDefault false;
+  # This makes `self` available in the NixOS configuration of our virtual machines.
+  # This is useful for referencing modules or packages from your own flake
+  # as well as importing from other flakes.
+  node.specialArgs = { inherit self; };
+  imports = [ test ];
+}).config.result

test/test.nix

@@ -0,0 +1,21 @@
+# ./tests/hello-world-server.nix
+(import ./lib.nix) {
+  name = "from-nixos";
+  nodes = {
+    # `self` here is set by using specialArgs in `lib.nix`
+    node1 = { self, pkgs, ... }: {
+      imports = [ self.nixosModules.malobeo-tasklist ];
+
+      services.malobeo-tasklist.enable = true;
+      environment.systemPackages = [ pkgs.curl ];
+    };
+  };
+
+  testScript = ''
+    start_all() # wait for our service to start
+    node1.wait_for_unit("malobeo-tasklist")
+    output = node1.succeed("curl localhost:8080")
+    # Check if our webserver returns the expected result
+    assert "tasklist" in output, f"'{output}' does not contain 'Hello world'"
+  '';
+}