chore: import upstream snapshot with attribution

tests/utils/test_file_utils.py

@@ -0,0 +1,51 @@
+# Copyright (c) 2025, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# 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.
+
+from unittest.mock import patch
+
+import pytest
+
+from nemo.utils.file_utils import robust_copy
+
+
+class TestRobustCopy:
+    @pytest.mark.unit
+    def test_robust_copy_success(self, tmp_path):
+        """Tests that robust_copy uses shutil.copy2 and does not fall back."""
+        src_file = tmp_path / "source.txt"
+        src_file.write_text("test content")
+        dest_file = tmp_path / "dest.txt"
+
+        with (
+            patch('nemo.utils.file_utils.shutil.copy2') as mock_copy2,
+            patch('nemo.utils.file_utils.shutil.copy') as mock_copy,
+        ):
+            robust_copy(src_file, dest_file)
+            mock_copy2.assert_called_once_with(src_file, dest_file)
+            mock_copy.assert_not_called()
+
+    @pytest.mark.unit
+    def test_robust_copy_fallback(self, tmp_path):
+        """Tests that robust_copy falls back to shutil.copy if shutil.copy2 fails."""
+        src_file = tmp_path / "source.txt"
+        src_file.write_text("test content")
+        dest_file = tmp_path / "dest.txt"
+
+        with (
+            patch('nemo.utils.file_utils.shutil.copy2', side_effect=PermissionError("copy2 fails")) as mock_copy2,
+            patch('nemo.utils.file_utils.shutil.copy') as mock_copy,
+        ):
+            robust_copy(src_file, dest_file)
+            mock_copy2.assert_called_once_with(src_file, dest_file)
+            mock_copy.assert_called_once_with(src_file, dest_file)