anchor.diff:    checkInputs = [
       pytestCheckHook
       pytest-mock
  +    pytest-xdist
  +  ];
  +
  +  pytestFlagsArray = [
  +    "--numprocesses $NIX_BUILD_CORES"
  +    "-m 'not network'"
     ];
   
     preCheck = "HOME=$TMPDIR";
   
     disabledTests = [
  -    # these may eventually succeed but are incredibly slow due to contacting
  -    # the internet
  -    "test_convert_requirements_file_without_name"
  -    "test_add_dependency_from_multiple_parents"
  -    "test_add_editable_package"
  -    "test_add_package"
  -    "test_add_package_with_mismatch_marker"
  -    "test_add_with_dry_run"
  -    "test_add_with_prerelease"
  -    "test_build_src_package_by_include"
  -    "test_editable_package_override_non_editable"
  -    "test_find_candidates_from_find_links"
  -    "test_freeze_dependencies_list"
  -    "test_info_global_project"
  -    "test_install_with_dry_run"
  -    "test_install_with_lockfile"
  -    "test_list_dependency_graph"
  -    "test_list_dependency_graph_with_circular_forward"
  -    "test_list_dependency_graph_with_circular_reverse"
  -    "test_list_reverse_dependency_graph"
  -    "test_load_multiple_plugings"
  -    "test_old_entry_point_compatibility"
  -    "test_parse_flit_project_metadata"
  -    "test_parse_local_directory_metadata"
  -    "test_parse_project_file_on_build_error"
  -    "test_parse_project_file_on_build_error_no_dep"
  -    "test_parse_project_file_on_build_error_with_extras"
  -    "test_parse_vcs_metadata"
  -    "test_post_lock_and_install_signals"
  -    "test_remove_both_normal_and_editable_packages"
  -    "test_remove_package"
  -    "test_remove_package_exist_in_multi_groups"
  -    "test_remove_package_no_sync"
  -    "test_remove_package_not_exist"
  -    "test_remove_package_with_dry_run"
  -    "test_resolve_file_req_with_prerelease"
  -    "test_resolve_local_and_named_requirement"
  -    "test_resolve_two_extras_from_the_same_package"
  -    "test_resolve_vcs_and_local_requirements"
  -    "test_sync_clean_packages"
  -    "test_sync_dry_run"
  -    "test_sync_packages_with_group_all"
  -    "test_sync_packages_with_groups"
  -    "test_sync_production_packages"
  -    "test_update_all_packages"
  -    "test_update_dry_run"
  -    "test_update_existing_package_with_prerelease"
  -    "test_update_ignore_constraints"
  -    "test_update_packages_with_top"
  -    "test_update_top_packages_dry_run"
  -    "test_update_with_package_and_groups_argument"
  -    # requires the internet
  -    "test_actual_list_freeze"
  -    "test_add_cached_vcs_requirement"
  -    "test_add_remote_package_url"
  -    "test_basic_integration"
  -    "test_build_distributions"
  -    "test_build_ignoring_pip_environment"
  -    "test_build_legacy_package"
  -    "test_build_package"
  -    "test_build_package_include"
  -    "test_build_single_module"
  -    "test_build_single_module_with_readme"
  -    "test_build_src_package"
  -    "test_build_with_config_settings"
  -    "test_build_with_no_isolation"
  -    "test_cache_egg_info_sdist"
  -    "test_cache_vcs_immutable_revision"
  -    "test_cli_build_with_config_settings"
  -    "test_expand_project_root_in_url"
  -    "test_extras_warning"
  -    "test_hash_cache"
  -    "test_install_wheel_with_cache"
  -    "test_install_wheel_with_data_scripts"
  -    "test_install_wheel_with_inconsistent_dist_info"
  -    "test_install_with_file_existing"
  -    "test_parse_abnormal_specifiers"
  -    "test_parse_artifact_metadata"
  -    "test_parse_metadata_with_extras"
  -    "test_parse_remote_link_metadata"
  -    "test_pep582_launcher_for_python_interpreter"
  -    "test_rollback_after_commit"
  -    "test_run_with_another_project_root"
  -    "test_search_package"
  -    "test_show_update_hint"
  -    "test_sync_only_different"
  -    "test_sync_with_index_change"
  -    "test_uninstall_commit_rollback"
  -    "test_uninstall_with_console_scripts"
  -    "test_update_with_prerelease_without_package_argument"
  -    "test_url_requirement_is_not_cached"
       # sys.executable and expected executable are different
       "test_set_non_exist_python_path"
  -    # editable inside nixpkgs doesn't seem to be a thing
  -    "test_vcs_candidate_in_subdirectory"
  -    # pdm compares with what looks to be an older version of poetry
  -    "test_parse_poetry_project_metadata"
       # pythonfinder isn't aware of nix's python infrastructure
       "test_auto_isolate_site_packages"
       "test_use_invalid_wrapper_python"
       "test_use_wrapper_python"
  -    # broken but wouldn't succeed anyway because of the network
  -    "test_sync_in_sequential_mode"
       # tries to read/write files without proper permissions
       "test_completion_command"
       "test_plugin_add"
       "test_plugin_list"
       "test_plugin_remove"
  -    # unknown breakage, but probably hitting the internet
  -    "test_show_package_on_pypi"
       # tries to treat a gzip file as a zipfile and fails
       "test_resolve_local_artifacts"
     ];
  
positive.code:   #
    # the patch is necessary because the fixture is creating a project and
    # doesn't appear to respect the settings in `$HOME`; possibly a bug upstream
    patches = [ ./check-update.patch ];
  
    propagatedBuildInputs = [
      blinker
  
negative.code: { lib, python3, fetchFromGitHub, fetchurl }:
  let
    python = python3.override {
      # override resolvelib due to
  