core/pkgs/build-support/trivial-builders/test/writeStringReferencesToFile.nix

{ callPackage, lib, pkgs, runCommand, samples, writeText
, writeStringReferencesToFile }:
let
  samplePaths = lib.unique (lib.attrValues samples);
  stri = x: "${x}";
  sampleText = writeText "sample-text"
    (lib.concatStringsSep "\n" (lib.unique (map stri samplePaths)));
  stringReferencesText = writeStringReferencesToFile
    ((lib.concatMapStringsSep "fillertext" stri (lib.attrValues samples)) + ''
      STORE=${builtins.storeDir};\nsystemctl start bar-foo.service
    '');
in runCommand "test-writeStringReferencesToFile" { } ''
  diff -U3 <(sort ${stringReferencesText}) <(sort ${sampleText})
  touch $out
''