Add test for chunked IF response reading

tests/test_if_session.py

@@ -782,3 +782,36 @@ async def test_do_restore_handles_stdout_read_failure(tmp_path):
 
     # Should return empty string on failure (player starts fresh)
     assert result == ""
+
+
+@pytest.mark.asyncio
+async def test_read_response_handles_chunked_data():
+    """_read_response() correctly handles data arriving in chunks."""
+    player = MagicMock()
+    session = IFSession(player, "/path/to/story.z5")
+
+    mock_process = AsyncMock()
+    mock_process.stdout = AsyncMock()
+    session.process = mock_process
+
+    # Data arrives in multi-byte chunks, last chunk includes prompt
+    chunks = [
+        b"Welcome to Zork.\n",
+        b"West of House\nYou are standing ",
+        b"in an open field.\n>",
+    ]
+    chunk_iter = iter(chunks)
+
+    async def read_chunked(n):
+        try:
+            return next(chunk_iter)
+        except StopIteration:
+            return b""
+
+    mock_process.stdout.read = AsyncMock(side_effect=read_chunked)
+
+    result = await session._read_response()
+
+    assert "Welcome to Zork" in result
+    assert "open field" in result
+    assert not result.strip().endswith(">")