Remove obsolete cross-device checkpoint test

The test verified the EXDEV/PermissionError workaround in _atomic_save that handled fsspec's cross-device staging. Since #21744 stages local checkpoints next to the destination, that code path is unreachable for local files — the test's mocks (os.rename, os.chmod) never fire on the new code path, leaving the test inert.

Author: c-pozzi

tests/tests_pytorch/trainer/connectors/test_checkpoint_connector.py

@@ -11,16 +11,12 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-import errno
-import operator
 import os
-import re
 from unittest import mock
 from unittest.mock import ANY, Mock
 
 import pytest
 import torch
-from lightning_utilities.core.imports import compare_version
 
 from lightning.pytorch import Trainer
 from lightning.pytorch.callbacks import Callback, ModelCheckpoint
@@ -109,31 +105,6 @@ def test_hpc_max_ckpt_version(tmp_path):
     )
 
 
-def test_local_cross_device_checkpoint(tmpdir):
-    """Test that the _CheckpointConnector can write local cross-device files or raises an error if fsspec<2025.5.0."""
-    model = BoringModel()
-    # hardcoding dir since `tmp_path` can be windows path
-    trainer = Trainer(
-        default_root_dir="memory://test_ckpt_for_fsspec", limit_train_batches=1, limit_val_batches=1, max_epochs=1
-    )
-    trainer.fit(model)
-    # Simulate the behavior of fsspec when writing to a local file system but other device.
-    with (
-        mock.patch("os.rename", side_effect=OSError(errno.EXDEV, "Invalid cross-device link")),
-        mock.patch("os.chmod", side_effect=PermissionError("Operation not permitted")),
-    ):
-        if compare_version("fsspec", operator.lt, "2025.5.0"):
-            with pytest.raises(
-                RuntimeError,
-                match=re.escape(
-                    'Upgrade fsspec to enable cross-device local checkpoints: pip install "fsspec[http]>=2025.5.0"'
-                ),
-            ):
-                trainer.save_checkpoint(tmpdir + "/test_ckpt_for_fsspec/hpc_ckpt.ckpt")
-        else:
-            trainer.save_checkpoint(tmpdir + "/test_ckpt_for_fsspec/hpc_ckpt.ckpt")
-
-
 def test_ckpt_for_fsspec():
     """Test that the _CheckpointConnector is able to write to fsspec file systems."""
     model = BoringModel()