Add unit tests for async module (AsyncConnection, AsyncCursor)

The async module had zero test coverage. Add tests for state
management, closed checks, context managers, iteration, and
fetch behavior mirroring the sync test structure.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

tests/test_async_connection.py

@@ -0,0 +1,56 @@
+"""Tests for AsyncConnection class."""
+
+import pytest
+
+from dqlitedbapi.aio import connect
+from dqlitedbapi.aio.connection import AsyncConnection
+from dqlitedbapi.aio.cursor import AsyncCursor
+from dqlitedbapi.exceptions import InterfaceError
+
+
+class TestAsyncConnection:
+    def test_connect_function_returns_async_connection(self) -> None:
+        conn = connect("localhost:9001", database="test", timeout=5.0)
+        assert isinstance(conn, AsyncConnection)
+
+    def test_cursor_returns_async_cursor(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = conn.cursor()
+        assert isinstance(cursor, AsyncCursor)
+
+    @pytest.mark.asyncio
+    async def test_close_marks_connection_closed(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        await conn.close()
+        assert conn._closed
+
+    @pytest.mark.asyncio
+    async def test_cursor_on_closed_connection_raises(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        await conn.close()
+
+        with pytest.raises(InterfaceError, match="Connection is closed"):
+            conn.cursor()
+
+    @pytest.mark.asyncio
+    async def test_commit_on_closed_connection_raises(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        await conn.close()
+
+        with pytest.raises(InterfaceError, match="Connection is closed"):
+            await conn.commit()
+
+    @pytest.mark.asyncio
+    async def test_rollback_on_closed_connection_raises(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        await conn.close()
+
+        with pytest.raises(InterfaceError, match="Connection is closed"):
+            await conn.rollback()
+
+    def test_cursor_is_sync(self) -> None:
+        """cursor() is intentionally sync for SQLAlchemy compatibility."""
+        conn = AsyncConnection("localhost:9001")
+        cursor = conn.cursor()
+        # Verify it returns directly, not a coroutine
+        assert isinstance(cursor, AsyncCursor)

tests/test_async_cursor.py

@@ -0,0 +1,97 @@
+"""Tests for AsyncCursor class."""
+
+import pytest
+
+from dqlitedbapi.aio.connection import AsyncConnection
+from dqlitedbapi.aio.cursor import AsyncCursor
+from dqlitedbapi.exceptions import InterfaceError
+
+
+class TestAsyncCursor:
+    def test_description_initially_none(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        assert cursor.description is None
+
+    def test_rowcount_initially_minus_one(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        assert cursor.rowcount == -1
+
+    def test_arraysize_default(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        assert cursor.arraysize == 1
+
+    def test_arraysize_setter(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        cursor.arraysize = 10
+        assert cursor.arraysize == 10
+
+    def test_lastrowid_initially_none(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        assert cursor.lastrowid is None
+
+    @pytest.mark.asyncio
+    async def test_close_marks_cursor_closed(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        await cursor.close()
+        assert cursor._closed
+
+    @pytest.mark.asyncio
+    async def test_fetchone_on_closed_cursor_raises(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        await cursor.close()
+
+        with pytest.raises(InterfaceError, match="Cursor is closed"):
+            await cursor.fetchone()
+
+    @pytest.mark.asyncio
+    async def test_fetchone_no_rows_returns_none(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        # Simulate a query that returned zero rows
+        cursor._description = [("id", None, None, None, None, None, None)]
+        cursor._rows = []
+        result = await cursor.fetchone()
+        assert result is None
+
+    @pytest.mark.asyncio
+    async def test_fetchall_no_rows_returns_empty(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        cursor._description = [("id", None, None, None, None, None, None)]
+        cursor._rows = []
+        result = await cursor.fetchall()
+        assert result == []
+
+    @pytest.mark.asyncio
+    async def test_context_manager(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        async with AsyncCursor(conn) as cursor:
+            assert not cursor._closed
+        assert cursor._closed
+
+    @pytest.mark.asyncio
+    async def test_async_iterator(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        cursor._rows = [(1, "a"), (2, "b"), (3, "c")]
+        cursor._description = [("id", None, None, None, None, None, None)]
+
+        results = [row async for row in cursor]
+        assert results == [(1, "a"), (2, "b"), (3, "c")]
+
+    def test_setinputsizes_noop(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        cursor.setinputsizes([None, None])
+
+    def test_setoutputsize_noop(self) -> None:
+        conn = AsyncConnection("localhost:9001")
+        cursor = AsyncCursor(conn)
+        cursor.setoutputsize(100, 0)