code: def test_watch_failure(self, r):
      r["a"] = 1
      r["b"] = 2
  
      with r.pipeline() as pipe:
          pipe.watch("a", "b")
          r["b"] = 3
          pipe.multi()
          pipe.get("a")
          with pytest.raises(redis.WatchError):
              pipe.execute()
  
          assert not pipe.watching
  
imports: from contextlib import closing
  from unittest import mock
  import pytest
  import redis
  from .conftest import skip_if_server_version_lt, wait_for_command
label_desc: Use image node_id 15 for calling the TestPipeline obj's underlying member method code with example usage: obj.test_watch_failure(r) without return types