diff --git a/TODO b/TODO
index 440cd59..145c66f 100644
--- a/TODO
+++ b/TODO
@@ -178,7 +178,7 @@ Description: to shorten the namespace and also indicate that testing utilities
 ID: 12
 Type: feature
 Title: simplify testing.fixtures.mock_pkg
-Status: in-progress
+Status: done
 Priority: high
 Created: 2025-06-21
 Description: Only bootstrap a package mock with the minimum requirements for a
diff --git a/src/byteb4rb1e/testing/pytest/fixtures.py b/src/byteb4rb1e/testing/pytest/fixtures.py
index b9ca0cb..7c93041 100644
--- a/src/byteb4rb1e/testing/pytest/fixtures.py
+++ b/src/byteb4rb1e/testing/pytest/fixtures.py
@@ -7,6 +7,8 @@ import pytest
 
 from byteb4rb1e.testing.pytest import get_current_test
 
+_SITE_PACKAGE_COUNTER: Dict[str, int] = {}
+
 
 @pytest.fixture
 def current_test() -> Tuple[Path, str]:
@@ -16,25 +18,27 @@ def current_test() -> Tuple[Path, str]:
 
 
 @pytest.fixture
-def mock_pkg(tmp_path):
-    def _create(name: str, files: Dict[str, Union[str, bytes]]):
-        pkg_path = tmp_path / name.replace('.', os.path.sep)
+def mock_system_site_package_dir(tmp_path):
+    global _SITE_PACKAGE_COUNTER
+
+    package_id = _SITE_PACKAGE_COUNTER.setdefault(tmp_path, 0)
+    _SITE_PACKAGE_COUNTER[tmp_path] += 1
+
+    sys_path = tmp_path / str(package_id)
+
+    def _create(name: str) -> Path:
+        pkg_path = sys_path / name.replace('.', os.path.sep)
+
         pkg_path.mkdir(parents=True)
+
         (pkg_path / "__init__.py").touch()
 
-        for fname, content in files.items():
-            fpath = (pkg_path / fname)
-            fpath.parent.mkdir(parents=True, exist_ok=True)
-            if isinstance(content, str):
-                fpath.write_text(content)
-            else:
-                fpath.write_bytes(content)
+        sys.path.insert(0, str(sys_path))
 
-        sys.path.insert(0, str(tmp_path))
-        return name, pkg_path
+        return pkg_path
 
     yield _create
 
     # cleanup sys.path after test
-    if str(tmp_path) in sys.path:
-        sys.path.remove(str(tmp_path))
+    if str(sys_path) in sys.path:
+        sys.path.remove(str(sys_path))
diff --git a/tests/integration/byteb4rb1e/testing/pytest/test_fixtures.py b/tests/integration/byteb4rb1e/testing/pytest/test_fixtures.py
index 0e0c5d9..a08851d 100644
--- a/tests/integration/byteb4rb1e/testing/pytest/test_fixtures.py
+++ b/tests/integration/byteb4rb1e/testing/pytest/test_fixtures.py
@@ -6,7 +6,10 @@ import pytest
 pytestmark = pytest.mark.pytest
 
 from byteb4rb1e.testing.pytest.decorators import run_in_subprocess_once
-from byteb4rb1e.testing.pytest.fixtures import current_test, mock_pkg
+from byteb4rb1e.testing.pytest.fixtures import (
+    current_test,
+    mock_system_site_package_dir
+)
 
 
 def test_current_test(current_test):
@@ -19,14 +22,16 @@ def test_current_test(current_test):
 
 
 @run_in_subprocess_once()
-def test_mock_pkg(mock_pkg):
+def test_mock_system_site_package_dir(mock_system_site_package_dir):
     """
     """
     dummy_data = 'Hello'
 
-    mock_pkg('foobarpkg', {
-        'data.txt': dummy_data
-    })
+    pkgdir = mock_system_site_package_dir('foobarpkg')
+
+    (pkgdir / 'data.txt').write_text(dummy_data)
+
+    assert (pkgdir / '__init__.py').exists()
 
     result = next(importlib.resources.files('foobarpkg').glob('data.txt')).read_text()