diff --git a/swh/storage/__init__.py b/swh/storage/__init__.py
--- a/swh/storage/__init__.py
+++ b/swh/storage/__init__.py
@@ -3,6 +3,7 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+
 from . import storage
 
 Storage = storage.Storage
@@ -12,15 +13,16 @@
     pass
 
 
+STORAGE_IMPLEMENTATION = {'local', 'remote', 'memory'}
+
+
 def get_storage(cls, args):
-    """
-    Get a storage object of class `storage_class` with arguments
+    """Get a storage object of class `storage_class` with arguments
     `storage_args`.
 
     Args:
         storage (dict): dictionary with keys:
-        - cls (str): storage's class, either 'local', 'remote',
-                     or 'memory'
+        - cls (str): storage's class, either local, remote, memory
         - args (dict): dictionary with keys
 
     Returns:
@@ -30,6 +32,9 @@
         ValueError if passed an unknown storage class.
 
     """
+    if cls not in STORAGE_IMPLEMENTATION:
+        raise ValueError('Unknown storage class `%s`. Supported: %s' % (
+            cls, ', '.join(STORAGE_IMPLEMENTATION)))
 
     if cls == 'remote':
         from .api.client import RemoteStorage as Storage
@@ -37,7 +42,5 @@
         from .storage import Storage
     elif cls == 'memory':
         from .in_memory import Storage
-    else:
-        raise ValueError('Unknown storage class `%s`' % cls)
 
     return Storage(**args)
diff --git a/swh/storage/tests/test_init.py b/swh/storage/tests/test_init.py
new file mode 100644
--- /dev/null
+++ b/swh/storage/tests/test_init.py
@@ -0,0 +1,42 @@
+# Copyright (C) 2019 The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+import pytest
+
+from unittest.mock import patch
+
+from swh.storage import get_storage
+
+from swh.storage.api.client import RemoteStorage
+from swh.storage.storage import Storage as DbStorage
+from swh.storage.in_memory import Storage as MemoryStorage
+
+
+@patch('swh.storage.storage.psycopg2.pool')
+def test_get_storage(mock_pool):
+    """Instantiating an existing storage should be ok
+
+    """
+    mock_pool.ThreadedConnectionPool.return_value = None
+    for cls, real_class, dummy_args in [
+            ('remote', RemoteStorage, {'url': 'url'}),
+            ('memory', MemoryStorage, {}),
+            ('local', DbStorage, {
+                'db': 'postgresql://db', 'objstorage': {
+                    'cls': 'memory', 'args': {},
+                },
+            }),
+    ]:
+        actual_storage = get_storage(cls, args=dummy_args)
+        assert actual_storage is not None
+        assert isinstance(actual_storage, real_class)
+
+
+def test_get_storage_failure():
+    """Instantiating an unknown storage should raise
+
+    """
+    with pytest.raises(ValueError, match='Unknown storage class `unknown`'):
+        get_storage('unknown', args=[])