{
  pkgs,
  inputs,
  self,
}: let
  localPackages = import ../pkgs {inherit pkgs inputs;};
  mkPkgs = overlays:
    import inputs.nixpkgs {
      system = pkgs.stdenv.hostPlatform.system;
      config.allowUnfree = true;
      inherit overlays;
    };

  upstreamPkgs = mkPkgs [];
  modifiedPkgs = mkPkgs [self.overlays.modifications];
  defaultPkgs = mkPkgs [self.overlays.default];

  expectedVersion = "2.29.8";
  expectedSrcHash = "sha256-+eiAdofrX1TRNFeD9MtTHt+XBH06c8NQHvTk6vrOU/k=";
  expectedPnpmHash = "sha256-j0IrYjVl83SzRo29rhEDCQLrt8kslWHdS7m4pG11DgA=";
  expectedChangelog = "https://github.com/n8n-io/n8n/releases/tag/n8n@${expectedVersion}";
  expectedXlsxTarball = "https://cdn.sheetjs.com/xlsx-0.20.2/xlsx-0.20.2.tgz";
  expectedRootNodeModuleSymlinks = [
    "ln -s .pnpm/node_modules/sass-embedded node_modules/sass-embedded"
    "ln -s .pnpm/node_modules/sqlite3 node_modules/sqlite3"
  ];

  checkN8nOverride = overlayName: package:
    if package.version != expectedVersion
    then throw "${overlayName} n8n version is ${package.version}, expected ${expectedVersion}"
    else if package.src.outputHash != expectedSrcHash
    then throw "${overlayName} n8n src hash is ${package.src.outputHash}, expected ${expectedSrcHash}"
    else if package.pnpmDeps.outputHash != expectedPnpmHash
    then throw "${overlayName} n8n pnpmDeps hash is ${package.pnpmDeps.outputHash}, expected ${expectedPnpmHash}"
    else if package.meta.changelog != expectedChangelog
    then throw "${overlayName} n8n changelog is ${package.meta.changelog}, expected ${expectedChangelog}"
    else "ok";

  checkBuildPhaseInherited = overlayName: package:
    if package.buildPhase != upstreamPkgs.n8n.buildPhase
    then throw "${overlayName} n8n buildPhase should be inherited from upstream nixpkgs"
    else "ok";

  checkRootNodeModuleSymlinks = overlayName: package:
    if !(pkgs.lib.all (symlink: pkgs.lib.hasInfix symlink (package.preBuild or "")) expectedRootNodeModuleSymlinks)
    then throw "${overlayName} n8n preBuild should create root node_modules symlinks required by the upstream buildPhase"
    else "ok";

  checkXlsxTarballLock = overlayName: package:
    pkgs.runCommand "${overlayName}-n8n-xlsx-tarball-lock-test" {
      inherit expectedXlsxTarball;
    } ''
      grep -F "xlsx@$expectedXlsxTarball:" ${package.src}/pnpm-lock.yaml
      grep -F "resolution: {tarball: $expectedXlsxTarball}" ${package.src}/pnpm-lock.yaml
      touch $out
    '';
in
  pkgs.runCommand "n8n-overlay-test" {
    n8nOverlayFile =
      if builtins.pathExists ../overlays/mods/n8n.nix
      then "ok"
      else throw "n8n overlay override must live in overlays/mods/n8n.nix";
    localN8nAbsent =
      if localPackages ? n8n
      then throw "pkgs/default.nix must not export a local n8n package"
      else "ok";
    modificationsOverlayN8n = checkN8nOverride "overlays.modifications" modifiedPkgs.n8n;
    defaultOverlayN8n = checkN8nOverride "overlays.default" defaultPkgs.n8n;
    modificationsOverlayBuildPhase = checkBuildPhaseInherited "overlays.modifications" modifiedPkgs.n8n;
    defaultOverlayBuildPhase = checkBuildPhaseInherited "overlays.default" defaultPkgs.n8n;
    modificationsOverlayRootNodeModuleSymlinks = checkRootNodeModuleSymlinks "overlays.modifications" modifiedPkgs.n8n;
    defaultOverlayRootNodeModuleSymlinks = checkRootNodeModuleSymlinks "overlays.default" defaultPkgs.n8n;
    modificationsOverlayXlsxTarballLock = checkXlsxTarballLock "overlays.modifications" modifiedPkgs.n8n;
    defaultOverlayXlsxTarballLock = checkXlsxTarballLock "overlays.default" defaultPkgs.n8n;
  } ''
    touch $out
  ''