chore(dataset): basic house-keeping (#3170)

tests/configs/test_default.py

@@ -0,0 +1,38 @@
+# Copyright 2026 The HuggingFace Inc. team. 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.
+import pytest
+
+from lerobot.configs.default import DatasetConfig
+
+
+def test_dataset_config_valid():
+    DatasetConfig(repo_id="user/repo", episodes=[0, 1, 2])
+
+
+def test_dataset_config_negative_episodes():
+    with pytest.raises(ValueError, match="non-negative"):
+        DatasetConfig(repo_id="user/repo", episodes=[0, -1, 2])
+
+
+def test_dataset_config_duplicate_episodes():
+    with pytest.raises(ValueError, match="duplicates"):
+        DatasetConfig(repo_id="user/repo", episodes=[0, 1, 1, 2])
+
+
+def test_dataset_config_none_episodes_ok():
+    DatasetConfig(repo_id="user/repo", episodes=None)
+
+
+def test_dataset_config_empty_episodes_ok():
+    DatasetConfig(repo_id="user/repo", episodes=[])

tests/datasets/test_image_writer.py

@@ -142,9 +142,9 @@ def test_write_image_image(tmp_path, img_factory):
 def test_write_image_exception(tmp_path):
     image_array = "invalid data"
     fpath = tmp_path / DUMMY_IMAGE
-    with patch("builtins.print") as mock_print:
+    with patch("lerobot.datasets.image_writer.logger") as mock_logger:
         write_image(image_array, fpath)
-        mock_print.assert_called()
+        mock_logger.error.assert_called()
         assert not fpath.exists()
 
 
@@ -243,10 +243,10 @@ def test_save_image_invalid_data(tmp_path):
         image_array = "invalid data"
         fpath = tmp_path / DUMMY_IMAGE
         fpath.parent.mkdir(parents=True, exist_ok=True)
-        with patch("builtins.print") as mock_print:
+        with patch("lerobot.datasets.image_writer.logger") as mock_logger:
             writer.save_image(image_array, fpath)
             writer.wait_until_done()
-            mock_print.assert_called()
+            mock_logger.error.assert_called()
             assert not fpath.exists()
     finally:
         writer.stop()

tests/datasets/test_sampler.py

@@ -13,6 +13,9 @@
 # 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 logging
+
+import pytest
 import torch
 from datasets import Dataset
 
@@ -106,3 +109,28 @@ def test_shuffle():
     assert sampler.indices == [0, 1, 2, 3, 4, 5]
     assert len(sampler) == 6
     assert set(sampler) == {0, 1, 2, 3, 4, 5}
+
+
+def test_negative_drop_first_frames_raises():
+    with pytest.raises(ValueError, match="drop_n_first_frames must be >= 0"):
+        EpisodeAwareSampler([0], [10], drop_n_first_frames=-1)
+
+
+def test_negative_drop_last_frames_raises():
+    with pytest.raises(ValueError, match="drop_n_last_frames must be >= 0"):
+        EpisodeAwareSampler([0], [10], drop_n_last_frames=-1)
+
+
+def test_all_episodes_dropped_raises():
+    # All episodes have 1 frame, drop_n_first_frames=1 removes all
+    with pytest.raises(ValueError, match="No valid frames remain"):
+        EpisodeAwareSampler([0, 1, 2], [1, 2, 3], drop_n_first_frames=1)
+
+
+def test_partial_episode_drop_warns(caplog):
+    # Episode 0: 1 frame (dropped), Episode 1: 5 frames (kept)
+    with caplog.at_level(logging.WARNING, logger="lerobot.datasets.sampler"):
+        sampler = EpisodeAwareSampler([0, 1], [1, 6], drop_n_first_frames=1)
+    # Episode 0 is skipped (1 frame, drop 1), Episode 1 keeps frames 2-5
+    assert sampler.indices == [2, 3, 4, 5]
+    assert "Episode 0" in caplog.text