Harden SQLite connection defaults with WAL and busy timeout

backend/tests/test_db.py

@@ -0,0 +1,58 @@
+import asyncio
+from pathlib import Path
+
+import aiosqlite
+
+from app.db import open_db
+
+
+async def test_open_db_applies_hardening_pragmas(tmp_path: Path) -> None:
+    database_path = str(tmp_path / "bangui_test.db")
+    db = await open_db(database_path)
+    try:
+        async with db.execute("PRAGMA journal_mode;") as cursor:
+            row = await cursor.fetchone()
+        assert row is not None and row[0].lower() == "wal"
+
+        async with db.execute("PRAGMA foreign_keys;") as cursor:
+            row = await cursor.fetchone()
+        assert row is not None and row[0] == 1
+
+        async with db.execute("PRAGMA busy_timeout;") as cursor:
+            row = await cursor.fetchone()
+        assert row is not None and row[0] == 5000
+    finally:
+        await db.close()
+
+
+async def test_open_db_respects_busy_timeout_for_concurrent_writes(tmp_path: Path) -> None:
+    database_path = str(tmp_path / "bangui_lock.db")
+    connection_a = await open_db(database_path)
+    try:
+        await connection_a.execute(
+            "CREATE TABLE IF NOT EXISTS test_lock (id INTEGER PRIMARY KEY, value TEXT);"
+        )
+        await connection_a.commit()
+
+        await connection_a.execute("BEGIN EXCLUSIVE;")
+
+        async def write_after_lock() -> None:
+            connection_b = await open_db(database_path)
+            try:
+                await connection_b.execute(
+                    "INSERT INTO test_lock (value) VALUES ('locked');"
+                )
+                await connection_b.commit()
+            finally:
+                await connection_b.close()
+
+        task = asyncio.create_task(write_after_lock())
+        await asyncio.sleep(0.1)
+        await connection_a.commit()
+        await task
+
+        async with connection_a.execute("SELECT value FROM test_lock;") as cursor:
+            row = await cursor.fetchone()
+        assert row is not None and row[0] == "locked"
+    finally:
+        await connection_a.close()