docstr: Test that storage.set() raises an exception when it fails to write to disk.
docstr_tok: ["Test","that","storage.set","(",")","raises","an","exception","when","it","fails","to","write","to","disk","."]
code: def test_storage_set_error(self):
      """Test that storage.set() raises an exception when it fails to write to disk."""
      with self.assertRaises(CacheStorageError) as e:
          self.storage.set("uniqueKey", b"new-value")
      self.assertEqual(str(e.exception), "Unable to write to cache")
  
imports: import logging
  import math
  import os.path
  import shutil
  import unittest
  from unittest.mock import MagicMock, patch
  from testfixtures import TempDirectory
  from streamlit import util
  from streamlit.logger import get_logger
  from streamlit.runtime.caching.storage import CacheStorageContext, CacheStorageError, CacheStorageKeyNotFoundError
  from streamlit.runtime.caching.storage.in_memory_cache_storage_wrapper import InMemoryCacheStorageWrapper
  from streamlit.runtime.caching.storage.local_disk_cache_storage import LocalDiskCacheStorage, LocalDiskCacheStorageManager
label_desc: Use image node_id 6 for calling the LocalDiskPersistCacheStorageTest obj's underlying member method code with example usage: obj.test_storage_set_error() without return types