Refactor radar system

python_app/tests/test_file_io.py

@@ -0,0 +1,44 @@
+"""Settings commits retain valid files on failure and concurrent writes."""
+
+from concurrent.futures import ThreadPoolExecutor
+import json
+from pathlib import Path
+import tempfile
+import unittest
+from unittest import mock
+
+from python_app.file_io import atomic_write_json
+from python_app.orchestration.gui_session_state import GuiSessionStateStore
+
+
+class AtomicJsonTest(unittest.TestCase):
+    def setUp(self) -> None:
+        directory = tempfile.TemporaryDirectory()
+        self.addCleanup(directory.cleanup)
+        self.path = Path(directory.name) / "settings.json"
+        atomic_write_json(self.path, {"old": True})
+
+    def test_failed_sync_or_commit_preserves_previous_file(self) -> None:
+        for operation in ('fsync', 'replace'):
+            with self.subTest(operation=operation), \
+                    mock.patch(f'python_app.file_io.os.{operation}', side_effect=OSError('disk failure')), \
+                    self.assertRaises(OSError):
+                atomic_write_json(self.path, {'new': True}, durable=True)
+            self.assertEqual(json.loads(self.path.read_text()), {'old': True})
+            self.assertEqual(list(self.path.parent.glob('*.tmp')), [])
+
+    def test_nonfinite_json_cannot_overwrite_settings(self) -> None:
+        with self.assertRaises(ValueError):
+            atomic_write_json(self.path, {'bad': float('nan')})
+        self.assertEqual(json.loads(self.path.read_text()), {'old': True})
+
+    def test_concurrent_writers_publish_complete_json_and_leave_no_temp_files(self) -> None:
+        payloads = [{'index': i, 'values': [i] * 1000} for i in range(32)]
+        with ThreadPoolExecutor(max_workers=8) as executor:
+            list(executor.map(lambda payload: atomic_write_json(self.path, payload), payloads))
+        self.assertIn(json.loads(self.path.read_text()), payloads)
+        self.assertEqual(list(self.path.parent.glob('*.tmp')), [])
+
+    def test_invalid_utf8_session_cache_uses_defaults(self) -> None:
+        self.path.write_bytes(b'\xff')
+        self.assertEqual(GuiSessionStateStore(self.path).load().last_profile_path, '')