docstr: Tests get_commit_id_from_cmd returns None if the command fails
docstr_tok: ["Tests","get_commit_id_from_cmd","returns","None","if","the","command","fails"]
code: def test_get_commit_id_from_cmd_returns_none_on_fail(self, mock):
      """
      Tests get_commit_id_from_cmd returns None if the command fails
      """
      not_sucessful = 255
      mock.side_effect = CalledProcessError(
          cmd="some command", returncode=not_sucessful
      )
      self.assertIsNone(get_commit_id_from_cmd())
  
imports: import unittest
  from unittest.mock import MagicMock, mock_open, patch
  from artifact_repository import *
label_desc: Use image node_id 2 for calling the TestArtifactRepositoryTool obj's underlying member method code with example usage: obj.test_get_commit_id_from_cmd_returns_none_on_fail(mock) without return types