slipshow: init nixos test (#434423)

nixos/tests/all-tests.nix

···
   simple = runTest ./simple.nix;
   sing-box = runTest ./sing-box.nix;
   slimserver = runTest ./slimserver.nix;
+  slipshow = runTest ./slipshow.nix;
   slurm = runTest ./slurm.nix;
   snmpd = runTest ./snmpd.nix;
   smokeping = runTest ./smokeping.nix;

nixos/tests/slipshow.nix

···
+{
+  lib,
+  pkgs,
+  ...
+}:
+{
+  name = "slipshow presentation test";
+
+  meta.maintainers = with lib.maintainers; [ ethancedwards8 ];
+
+  nodes.machine = {
+    environment.systemPackages = with pkgs; [ slipshow ];
+
+    environment.etc."slipshow".source = pkgs.fetchFromGitHub {
+      owner = "meithecatte";
+      repo = "bbslides";
+      rev = "ce1c08cafa71ae36dda8cc581956548b8386ae16";
+      hash = "sha256-sOydmvtDeMhNejDkwlsXdrbwtqN6lcNnzTnGzBVRFxA=";
+    };
+  };
+
+  testScript =
+    { nodes, ... }:
+    ''
+      start_all()
+
+      # it may take around a minute to compile the file and serve it
+      machine.succeed("slipshow serve /etc/slipshow/bbslides.md &>/dev/null &")
+
+      # slipshow serves defaultly on :8080 and unfortunately cannot
+      # be changed currently
+      machine.wait_for_open_port(8080)
+      machine.succeed("curl -i 0.0.0.0:8080")
+    '';
+}

pkgs/by-name/sl/slipshow/package.nix

···
   ocamlPackages,
   fetchFromGitHub,
   versionCheckHook,
+  nixosTests,
   nix-update-script,
 }:
 
···
   versionCheckProgramArg = "--version";
   doInstallCheck = true;
 
-  passthru.updateScript = nix-update-script { };
+  passthru = {
+    tests = { inherit (nixosTests) slipshow; };
+    updateScript = nix-update-script { };
+  };
 
   meta = {
     description = "Engine for displaying slips, the next-gen version of slides";