{ pkgs, pkgsLinux, buildPackages, lib, callPackage, runCommand, stdenv
, substituteAll, testers }:
# Documentation is in doc/builders/testers.chapter.md
{
  # See https://nixos.org/manual/nixpkgs/unstable/#tester-testBuildFailure
  # or doc/builders/testers.chapter.md
  testBuildFailure = drv:
    drv.overrideAttrs (orig: {
      builder = buildPackages.bash;
      args = [
        (substituteAll {
          coreutils = buildPackages.coreutils;
          src = ./expect-failure.sh;
        })
        orig.realBuilder or stdenv.shell
      ] ++ orig.args or [
        "-e"
        (orig.builder or ../../stdenv/generic/default-builder.sh)
      ];
    });

  # See https://nixos.org/manual/nixpkgs/unstable/#tester-testEqualDerivation
  # or doc/builders/testers.chapter.md
  testEqualDerivation = callPackage ./test-equal-derivation.nix { };

  # See https://nixos.org/manual/nixpkgs/unstable/#tester-testEqualContents
  # or doc/builders/testers.chapter.md
  testEqualContents = { assertion, actual, expected, }:
    runCommand "equal-contents-${lib.strings.toLower assertion}" {
      inherit assertion actual expected;
    } ''
      echo "Checking:"
      echo "$assertion"
      if ! diff -U5 -r "$actual" "$expected" --color=always
      then
        echo
        echo 'Contents must be equal, but were not!'
        echo
        echo "+: expected,   at $expected"
        echo "-: unexpected, at $actual"
        exit 1
      else
        find "$expected" -type f -executable > expected-executables | sort
        find "$actual" -type f -executable > actual-executables | sort
        if ! diff -U0 actual-executables expected-executables --color=always
        then
          echo
          echo "Contents must be equal, but some files' executable bits don't match"
          echo
          echo "+: make this file executable in the actual contents"
          echo "-: make this file non-executable in the actual contents"
          exit 1
        else
          echo "expected $expected and actual $actual match."
          echo 'OK'
          touch $out
        fi
      fi
    '';

  # See https://nixos.org/manual/nixpkgs/unstable/#tester-testVersion
  # or doc/builders/testers.chapter.md
  testVersion = { package, command ?
      "${package.meta.mainProgram or package.pname or package.name} --version"
    , version ? package.version, }:
    runCommand "${package.name}-test-version" {
      nativeBuildInputs = [ package ];
      meta.timeout = 60;
    } ''
      if output=$(${command} 2>&1); then
        if grep -Fw -- "${version}" - <<< "$output"; then
          touch $out
        else
          echo "Version string '${version}' not found!" >&2
          echo "The output was:" >&2
          echo "$output" >&2
          exit 1
        fi
      else
        echo -n ${lib.escapeShellArg command} >&2
        echo " returned a non-zero exit code." >&2
        echo "$output" >&2
        exit 1
      fi
    '';

  # See doc/builders/testers.chapter.md or
  # https://nixos.org/manual/nixpkgs/unstable/#tester-invalidateFetcherByDrvHash
  invalidateFetcherByDrvHash = f: args:
    let
      drvPath = (f args).drvPath;
      # It's safe to discard the context, because we don't access the path.
      salt = builtins.unsafeDiscardStringContext
        (lib.substring 0 12 (baseNameOf drvPath));
      # New derivation incorporating the original drv hash in the name
      salted =
        f (args // { name = "${args.name or "source"}-salted-${salt}"; });
      # Make sure we did change the derivation. If the fetcher ignores `name`,
      # `invalidateFetcherByDrvHash` doesn't work.
      checked = if salted.drvPath == drvPath then
        throw
        "invalidateFetcherByDrvHash: Adding the derivation hash to the fixed-output derivation name had no effect. Make sure the fetcher's name argument ends up in the derivation name. Otherwise, the fetcher will not be re-run when its implementation changes. This is important for testing."
      else
        salted;
    in checked;

  # See doc/builders/testers.chapter.md or
  # https://nixos.org/manual/nixpkgs/unstable/#tester-runNixOSTest
  runNixOSTest = let nixos = import ../../../nixos/lib { inherit lib; };
  in testModule:
  nixos.runTest {
    _file = "pkgs.runNixOSTest implementation";
    imports = [
      (lib.setDefaultModuleLocation
        "the argument that was passed to pkgs.runNixOSTest" testModule)
    ];
    hostPkgs = pkgs;
    node.pkgs = pkgsLinux;
  };

  # See doc/builders/testers.chapter.md or
  # https://nixos.org/manual/nixpkgs/unstable/#tester-invalidateFetcherByDrvHash
  nixosTest = let
    # The nixos/lib/testing-python.nix module, preapplied with arguments that
    # make sense for this evaluation of Nixpkgs.
    nixosTesting = (import ../../../nixos/lib/testing-python.nix {
      inherit (stdenv.hostPlatform) system;
      inherit pkgs;
      extraConfigurations =
        [ ({ lib, ... }: { config.nixpkgs.pkgs = lib.mkDefault pkgsLinux; }) ];
    });
  in test:
  let
    loadedTest = if builtins.typeOf test == "path" then import test else test;
    calledTest = lib.toFunction loadedTest pkgs;
  in nixosTesting.simpleTest calledTest;

  hasPkgConfigModule = { moduleName, ... }@args:
    lib.warn
    "testers.hasPkgConfigModule has been deprecated in favor of testers.hasPkgConfigModules. It accepts a list of strings via the moduleNames argument instead of a single moduleName."
    (testers.hasPkgConfigModules (builtins.removeAttrs args [ "moduleName" ]
      // {
        moduleNames = [ moduleName ];
      }));
  hasPkgConfigModules = callPackage ./hasPkgConfigModules/tester.nix { };

  testMetaPkgConfig = callPackage ./testMetaPkgConfig/tester.nix { };
}