{ python
, runCommand
, substituteAll
, lib
, callPackage
}:

let
  envs = let
    inherit python;
    pythonEnv = python.withPackages(ps: with ps; [ ]);
    pythonVirtualEnv = python.withPackages(ps: with ps; [ virtualenv ]);
  in {
    # Plain Python interpreter
    plain = rec {
      env = python;
      interpreter = env.interpreter;
      is_venv = "False";
      is_nixenv = "False";
      is_virtualenv = "False";
    };
  } // lib.optionalAttrs (python.isPy3k && !python.isPyPy) {
    # Use virtualenv from a Nix env.
    # Does not function with Python 2
    # ValueError: source and destination is the same /nix/store/38kz3j1a87cq5y59k5w7k9yk4cqgc5b2-python-2.7.18/lib/python2.7/os.py
    nixenv-virtualenv = rec {
      env = runCommand "${python.name}-virtualenv" {} ''
        ${pythonVirtualEnv.interpreter} -m virtualenv $out
      '';
      interpreter = "${env}/bin/${python.executable}";
      is_venv = "False";
      is_nixenv = "True";
      is_virtualenv = "True";
    };
  } // lib.optionalAttrs (python.implementation != "graal") {
    # Python Nix environment (python.buildEnv)
    nixenv = rec {
      env = pythonEnv;
      interpreter = env.interpreter;
      is_venv = "False";
      is_nixenv = "True";
      is_virtualenv = "True";
    };
  } // lib.optionalAttrs (python.isPy3k && (!python.isPyPy)) rec {
    # Venv built using plain Python
    # Python 2 does not support venv
    # TODO: PyPy executable name is incorrect, it should be pypy-c or pypy-3c instead of pypy and pypy3.
    plain-venv = rec {
      env = runCommand "${python.name}-venv" {} ''
        ${python.interpreter} -m venv $out
      '';
      interpreter = "${env}/bin/${python.executable}";
      is_venv = "True";
      is_nixenv = "False";
      is_virtualenv = "True";
    };

  } // lib.optionalAttrs (python.pythonAtLeast "3.8") {
    # Venv built using Python Nix environment (python.buildEnv)
    # TODO: Cannot create venv from a  nix env
    # Error: Command '['/nix/store/ddc8nqx73pda86ibvhzdmvdsqmwnbjf7-python3-3.7.6-venv/bin/python3.7', '-Im', 'ensurepip', '--upgrade', '--default-pip']' returned non-zero exit status 1.
    nixenv-venv = rec {
      env = runCommand "${python.name}-venv" {} ''
        ${pythonEnv.interpreter} -m venv $out
      '';
      interpreter = "${env}/bin/${pythonEnv.executable}";
      is_venv = "True";
      is_nixenv = "True";
      is_virtualenv = "True";
    };
  };

  # All PyPy package builds are broken at the moment
  integrationTests = lib.optionalAttrs (python.pythonAtLeast "3.7"  && (!python.isPyPy)) rec {
    # Before the addition of NIX_PYTHONPREFIX mypy was broken with typed packages
    nix-pythonprefix-mypy = callPackage ./tests/test_nix_pythonprefix {
      interpreter = python;
    };
  };

  testfun = name: attrs: runCommand "${python.name}-tests-${name}" ({
    inherit (python) pythonVersion;
  } // attrs) ''
    cp -r ${./tests} tests
    chmod -R +w tests
    substituteAllInPlace tests/test_python.py
    ${attrs.interpreter} -m unittest discover --verbose tests #/test_python.py
    mkdir $out
    touch $out/success
  '';

in lib.mapAttrs testfun envs // integrationTests