Fix unit tests

tests/datasets/test_utils.py

@@ -14,12 +14,20 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import json
+from copy import deepcopy
+
 import torch
 from datasets import Dataset
 from huggingface_hub import DatasetCard
 
 from lerobot.common.datasets.push_dataset_to_hub.utils import calculate_episode_data_index
-from lerobot.common.datasets.utils import create_lerobot_dataset_card, hf_transform_to_torch
+from lerobot.common.datasets.utils import (
+    create_lerobot_dataset_card,
+    flatten_dict,
+    hf_transform_to_torch,
+    unflatten_dict,
+)
 
 
 def test_default_parameters():
@@ -53,3 +61,26 @@ def test_calculate_episode_data_index():
     episode_data_index = calculate_episode_data_index(dataset)
     assert torch.equal(episode_data_index["from"], torch.tensor([0, 2, 3]))
     assert torch.equal(episode_data_index["to"], torch.tensor([2, 3, 6]))
+
+
+def test_flatten_unflatten_dict():
+    d = {
+        "obs": {
+            "min": 0,
+            "max": 1,
+            "mean": 2,
+            "std": 3,
+        },
+        "action": {
+            "min": 4,
+            "max": 5,
+            "mean": 6,
+            "std": 7,
+        },
+    }
+
+    original_d = deepcopy(d)
+    d = unflatten_dict(flatten_dict(d))
+
+    # test equality between nested dicts
+    assert json.dumps(original_d, sort_keys=True) == json.dumps(d, sort_keys=True), f"{original_d} != {d}"