diff --git a/tests/test_tsdb.py b/tests/test_tsdb.py
index 677e36a..41e7fd6 100644
--- a/tests/test_tsdb.py
+++ b/tests/test_tsdb.py
@@ -14,6 +14,8 @@
 
 DATASETS_TO_TEST = [
     "ucr_uea_Wine",
+    "physionet_2012",
+    "beijing_multisite_air_quality",
 ]
 
 
@@ -40,7 +42,7 @@ def test_2_dataset_loading(self):
     def test_3_dataset_purging(self):
         cached_datasets = tsdb.list_cache()
         assert isinstance(cached_datasets, list)
-        tsdb.delete_cache("ucr_uea_Wine")  # delete single
+        tsdb.delete_cache("physionet_2012")  # delete single
         tsdb.delete_cache()  # delete all
 
     def test_4_logging(self):
diff --git a/tsdb/utils/downloading.py b/tsdb/utils/downloading.py
index 40fc9bc..5e629e6 100644
--- a/tsdb/utils/downloading.py
+++ b/tsdb/utils/downloading.py
@@ -85,7 +85,7 @@ def _download_and_extract(url: str, saving_path: str) -> Optional[str]:
     return saving_path
 
 
-def download_and_extract(dataset_name: str, dataset_saving_path: str) -> Optional[str]:
+def download_and_extract(dataset_name: str, dataset_saving_path: str) -> None:
     """Wrapper of _download_and_extract.
 
     Parameters
@@ -96,15 +96,11 @@ def download_and_extract(dataset_name: str, dataset_saving_path: str) -> Optiona
     dataset_saving_path : str,
         The local path for dataset saving.
 
-    Returns
-    -------
-    saving_path if successful else None
-
     """
     logger.info("Start downloading...")
     os.makedirs(dataset_saving_path)
     if isinstance(DATABASE[dataset_name], list):
         for link in DATABASE[dataset_name]:
-            return _download_and_extract(link, dataset_saving_path)
+            _download_and_extract(link, dataset_saving_path)
     else:
-        return _download_and_extract(DATABASE[dataset_name], dataset_saving_path)
+        _download_and_extract(DATABASE[dataset_name], dataset_saving_path)