diff --git a/requirements-test.txt b/requirements-test.txt
index e8e0b30..1b87a41 100644
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -1,3 +1,4 @@
 pytest
+pytest-mock
 swh.core[http] >= 0.0.61
 swh.scheduler[testing]
diff --git a/swh/loader/mercurial/tests/test_tasks.py b/swh/loader/mercurial/tests/test_tasks.py
index e130c42..6e050d7 100644
--- a/swh/loader/mercurial/tests/test_tasks.py
+++ b/swh/loader/mercurial/tests/test_tasks.py
@@ -1,40 +1,40 @@
-# Copyright (C) 2018  The Software Heritage developers
+# Copyright (C) 2018-2019  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
 
-from unittest.mock import patch
 
-
-@patch('swh.loader.mercurial.loader.HgBundle20Loader.load')
-def test_loader(mock_loader, swh_app, celery_session_worker):
+def test_loader(mocker, swh_app, celery_session_worker):
+    mock_loader = mocker.patch(
+        'swh.loader.mercurial.loader.HgBundle20Loader.load')
     mock_loader.return_value = {'status': 'eventful'}
 
     res = swh_app.send_task(
         'swh.loader.mercurial.tasks.LoadMercurial',
         (), dict(url='origin_url',
                  directory='/some/repo',
                  visit_date='now'))
     assert res
     res.wait()
     assert res.successful()
 
     assert res.result == {'status': 'eventful'}
     mock_loader.assert_called_once_with()
 
 
-@patch('swh.loader.mercurial.loader.HgArchiveBundle20Loader.load')
-def test_archive_loader(mock_loader, swh_app, celery_session_worker):
+def test_archive_loader(mocker, swh_app, celery_session_worker):
+    mock_loader = mocker.patch(
+        'swh.loader.mercurial.loader.HgArchiveBundle20Loader.load')
     mock_loader.return_value = {'status': 'uneventful'}
 
     res = swh_app.send_task(
         'swh.loader.mercurial.tasks.LoadArchiveMercurial',
         (), dict(url='another_url',
                  archive_path='/some/tar.tgz',
                  visit_date='now'))
     assert res
     res.wait()
     assert res.successful()
 
     assert res.result == {'status': 'uneventful'}
     mock_loader.assert_called_once_with()