[RFC PATCH 09/13] tests: replace NamedTemporaryFile with tmp_path in patatt fixture

Use pytest's built-in tmp_path fixture to store the ephemeral ed25519
private key instead of tempfile.NamedTemporaryFile.  This removes the
manual os.unlink teardown step (pytest removes the directory
automatically, even when a test raises) and also avoids the Windows
restriction that a NamedTemporaryFile with delete=True cannot be opened
by a second process while still open.

Signed-off-by: Adrian Neftali Sanchez <[email protected]>
---
 src/tests/test_patatt.py | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/src/tests/test_patatt.py b/src/tests/test_patatt.py
index de05277..3ed4711 100644
--- a/src/tests/test_patatt.py
+++ b/src/tests/test_patatt.py
@@ -6,6 +6,7 @@ Uses ephemeral ed25519 keys so no external key material is needed.
 import base64
 import email.message
 import os
+import pathlib
 import tempfile
 from collections.abc import Generator
 from typing import Tuple, Union
@@ -18,21 +19,29 @@ import patatt
 
 
 @pytest.fixture()
-def ed25519_keypair() -> Generator[Tuple[str, str, str, str], None, None]:
-    """Generate an ephemeral ed25519 keypair written to temp files.
-
-    Returns (privkey_path, verify_key_b64, identity, selector).
-    The private key file is written so patatt can find it via
-    signingkey = ed25519:/path/to/key.
+def ed25519_keypair(
+    tmp_path: pathlib.Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> Generator[Tuple[str, str, str, str], None, None]:
+    """Generate an ephemeral ed25519 keypair stored in patatt's data directory.
+
+    Returns (key_name, verify_key_b64, identity, selector).  The private key
+    is written to ``<tmp_path>/patatt/private/<key_name>.key``.  XDG_DATA_HOME
+    is pointed at ``tmp_path`` for the duration of the test so patatt resolves
+    the key by name without any OS-specific absolute-path handling.
+    patatt.KEYCACHE is cleared to prevent key material from a previous test
+    leaking into this one (all tests share the identity "[email protected]").
     """
     sk = SigningKey.generate()
     sk_b64 = base64.b64encode(sk.encode()).decode()
     vk_b64 = base64.b64encode(sk.verify_key.encode()).decode()
-    with tempfile.NamedTemporaryFile(mode='w', suffix='.key', delete=False) as fh:
-        fh.write(sk_b64)
-        privkey_path = fh.name
-    yield privkey_path, vk_b64, '[email protected]', 'default'
-    os.unlink(privkey_path)
+    key_name = 'test-key'
+    private_dir = tmp_path / 'patatt' / 'private'
+    private_dir.mkdir(parents=True, exist_ok=True)
+    (private_dir / f'{key_name}.key').write_text(sk_b64)
+    monkeypatch.setenv('XDG_DATA_HOME', str(tmp_path))
+    monkeypatch.setattr(patatt, 'KEYCACHE', {})
+    yield key_name, vk_b64, '[email protected]', 'default'
 
 
 @pytest.fixture()
-- 
2.45.0.windows.1