anchor.diff:    buildInputs = [ readline ];
   
     doCheck = true;
  +  checkInputs = [ bc ];
     checkPhase = ''
       python3 -m pytest test.py
     '';
  
positive.code: { stdenv, fetchFromGitHub, python3Packages, readline }:
  
  with stdenv.lib;
  
  stdenv.mkDerivation rec {
    pname = "bcal";
    version = "1.9";
  
    src = fetchFromGitHub {
      owner = "jarun";
      repo = "bcal";
      rev = "v${version}";
      sha256 = "0h6qi5rvzl6c6fsfdpdb3l4jcgip03l18i0b1x08z1y89i56y8mm";
    };
  
    nativeBuildInputs = [ python3Packages.pytest ];
  
negative.code:   meta = {
      description = "Storage conversion and expression calculator";
      homepage = "https://github.com/jarun/bcal";
      license = licenses.gpl3Only;
      platforms = [ "aarch64-linux" "x86_64-darwin" "x86_64-linux" ];
      maintainers = with maintainers; [ jfrankenau ];
    };
  