diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 1ae6e51..5c5db27 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -8,4 +8,7 @@ jobs:
     steps:
     - uses: actions/checkout@v2
     - uses: cachix/install-nix-action@v12
-    - run: nix-build -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixpkgs-unstable.tar.gz
+    - name: build
+      run: NIX_PATH=nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixpkgs-unstable.tar.gz nix-build
+    - name: Run tests
+      run: NIX_PATH=nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixpkgs-unstable.tar.gz nix-shell --command "py.test -s ."
diff --git a/default.nix b/default.nix
index 1f32712..6f38f1c 100644
--- a/default.nix
+++ b/default.nix
@@ -16,12 +16,11 @@ python3.pkgs.buildPythonApplication rec {
     mypy
     # technically not a test input, but we need it for development in PATH
     nixFlakes
+    nix-prefetch
   ];
   checkPhase = ''
     echo -e "\x1b[32m## run black\x1b[0m"
     LC_ALL=en_US.utf-8 black --check .
-    echo -e "\x1b[32m## run pytest\x1b[0m"
-    py.test -s .
     echo -e "\x1b[32m## run flake8\x1b[0m"
     flake8 nix_update
     echo -e "\x1b[32m## run mypy\x1b[0m"
diff --git a/nix_update/options.py b/nix_update/options.py
index 9b42a6c..0202aa5 100644
--- a/nix_update/options.py
+++ b/nix_update/options.py
@@ -3,12 +3,12 @@ from dataclasses import dataclass
 
 @dataclass
 class Options:
-    version: str
-    import_path: str
-    commit: bool
     attribute: str
-    shell: bool
-    run: bool
-    build: bool
-    test: bool
-    version_regex: str
+    version: str = "auto"
+    version_regex: str = "(.*)"
+    import_path: str = "./."
+    commit: bool = False
+    shell: bool = False
+    run: bool = False
+    build: bool = False
+    test: bool = False
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..f204d31
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+
+import pytest
+import sys
+from pathlib import Path
+from typing import Type, Iterator, Any
+import shutil
+import tempfile
+from contextlib import contextmanager
+
+
+TEST_ROOT = Path(__file__).parent.resolve()
+sys.path.append(str(TEST_ROOT.parent))
+
+
+class Helpers:
+    @staticmethod
+    def root() -> Path:
+        return TEST_ROOT
+
+    @staticmethod
+    @contextmanager
+    def testpkgs() -> Iterator[Path]:
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            shutil.copytree(
+                Helpers.root().joinpath("testpkgs"), tmpdirname, dirs_exist_ok=True
+            )
+            yield Path(tmpdirname)
+
+
+@pytest.fixture
+def helpers() -> Type[Helpers]:
+    return Helpers
diff --git a/tests/test_git.py b/tests/test_git.py
index a0a10e5..dcc118c 100644
--- a/tests/test_git.py
+++ b/tests/test_git.py
@@ -1,16 +1,14 @@
 #!/usr/bin/env python3
 
 from pathlib import Path
-from unittest import TestCase
 from nix_update.git import old_version_from_diff
-
+import conftest
 
 TEST_ROOT = Path(__file__).parent.resolve()
 
 
-class WordDiff(TestCase):
-    def test_worddiff(self) -> None:
-        with open(TEST_ROOT.joinpath("consul.patch")) as f:
-            diff = f.read()
+def test_worddiff(helpers: conftest.Helpers) -> None:
+    with open(helpers.root().joinpath("consul.patch")) as f:
+        diff = f.read()
         s = old_version_from_diff(diff, 5, "1.9.0")
-        self.assertEqual(s, "1.8.6")
+        assert s == "1.8.6"
diff --git a/tests/test_pypi.py b/tests/test_pypi.py
new file mode 100644
index 0000000..354a7d9
--- /dev/null
+++ b/tests/test_pypi.py
@@ -0,0 +1,27 @@
+#!/usr/bin/env python3
+
+from nix_update.options import Options
+from nix_update.update import update
+import subprocess
+import conftest
+
+
+def test_update(helpers: conftest.Helpers) -> None:
+    with helpers.testpkgs() as path:
+        opts = Options(attribute="pypi", import_path=path)
+        update(opts)
+        version = subprocess.run(
+            [
+                "nix",
+                "eval",
+                "--raw",
+                "--experimental-features",
+                "nix-command",
+                "-f",
+                path,
+                "pypi.version",
+            ],
+            text=True,
+            stdout=subprocess.PIPE,
+        )
+        assert version.stdout.strip() >= "3.0.1"
diff --git a/tests/testpkgs/default.nix b/tests/testpkgs/default.nix
new file mode 100644
index 0000000..2416a5d
--- /dev/null
+++ b/tests/testpkgs/default.nix
@@ -0,0 +1,4 @@
+{ pkgs ? import <nixpkgs> {} }:
+{
+  pypi = pkgs.python3.pkgs.callPackage ./pypi.nix {};
+}
diff --git a/tests/testpkgs/pypi.nix b/tests/testpkgs/pypi.nix
new file mode 100644
index 0000000..077e0ba
--- /dev/null
+++ b/tests/testpkgs/pypi.nix
@@ -0,0 +1,16 @@
+{ buildPythonPackage, fetchPypi, twisted, mock, pytestCheckHook }:
+
+buildPythonPackage rec {
+  pname = "python-mpd2";
+  version = "1.0.0";
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "0000000000000000000000000000000000000000000000000000";
+  };
+  checkInputs = [
+    pytestCheckHook
+    twisted
+    mock
+  ];
+  pytestFlagsArray = [ "mpd/tests.py" ];
+}