[mypy] Enable type checking for test directory (#5017)

tests/spec_decode/test_batch_expansion.py

@@ -1,3 +1,5 @@
+from typing import List
+
 import pytest
 import torch
 
@@ -38,14 +40,14 @@ def test_get_token_ids_to_score(k: int):
         device='cuda',
     )
 
-    expected_output = [
+    expected_output: List[List[int]] = [
         [],
     ]
     for i in range(proposal_token_ids.shape[0]):
         expected_output.append(proposal_token_ids[:i + 1].tolist())
 
     scorer = BatchExpansionTop1Scorer(mock_worker(), 'cuda:0', 32_000)
-    actual_output = scorer._get_token_ids_to_score(proposal_token_ids)  # pylint: disable=protected-access
+    actual_output = scorer._get_token_ids_to_score(proposal_token_ids.tolist())  # pylint: disable=protected-access
 
     actual_output = [
         x.tolist() if isinstance(x, torch.Tensor) else x for x in actual_output