diff --git a/swh/objstorage/tests/test_objstorage_azure.py b/swh/objstorage/tests/test_objstorage_azure.py
index c1576ff..7586e8e 100644
--- a/swh/objstorage/tests/test_objstorage_azure.py
+++ b/swh/objstorage/tests/test_objstorage_azure.py
@@ -1,76 +1,77 @@
 # Copyright (C) 2016  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
 
+from collections import defaultdict
 import unittest
+from unittest.mock import patch
 
 from azure.common import AzureMissingResourceHttpError
 
 from swh.objstorage.cloud.objstorage_azure import AzureCloudObjStorage
 
 from objstorage_testing import ObjStorageTestFixture
 
 
 class MockBlob():
     """ Libcloud object mock that replicates its API """
     def __init__(self, name, content):
         self.name = name
         self.content = content
 
 
 class MockBlockBlobService():
     """Mock internal azure library which AzureCloudObjStorage depends upon.
 
     """
     data = {}
 
-    def __init__(self, account_name, api_secret_key, container_name):
+    def __init__(self, account_name, account_key, **kwargs):
         # do not care for the account_name and the api_secret_key here
-        self.data[container_name] = {}
+        self.data = defaultdict(dict)
 
     def get_container_properties(self, container_name):
+        self.data[container_name]
         return container_name in self.data
 
     def create_blob_from_bytes(self, container_name, blob_name, blob):
         self.data[container_name][blob_name] = blob
 
     def get_blob_to_bytes(self, container_name, blob_name):
         if blob_name not in self.data[container_name]:
             raise AzureMissingResourceHttpError(
                 'Blob %s not found' % blob_name,
                 404)
         return MockBlob(name=blob_name,
                         content=self.data[container_name][blob_name])
 
     def delete_blob(self, container_name, blob_name):
         try:
             self.data[container_name].pop(blob_name)
         except KeyError:
             raise AzureMissingResourceHttpError(
                 'Blob %s not found' % blob_name, 404)
         return True
 
     def exists(self, container_name, blob_name):
         return blob_name in self.data[container_name]
 
     def list_blobs(self, container_name):
         for blob_name, content in self.data[container_name].items():
             yield MockBlob(name=blob_name, content=content)
 
 
-class MockAzureCloudObjStorage(AzureCloudObjStorage):
-    """ Cloud object storage that uses a mocked driver """
-    def __init__(self, api_key, api_secret_key, container_name):
-        self.container_name = container_name
-        self.block_blob_service = MockBlockBlobService(api_key, api_secret_key,
-                                                       container_name)
-        self.allow_delete = False
-
-
 class TestAzureCloudObjStorage(ObjStorageTestFixture, unittest.TestCase):
 
     def setUp(self):
         super().setUp()
-        self.storage = MockAzureCloudObjStorage(
+        patcher = patch(
+            'swh.objstorage.cloud.objstorage_azure.BlockBlobService',
+            MockBlockBlobService,
+        )
+        patcher.start()
+        self.addCleanup(patcher.stop)
+
+        self.storage = AzureCloudObjStorage(
             'account-name', 'api-secret-key', 'container-name')