diff --git a/setup.py b/setup.py
index 16202219d4..e60acbfdae 100755
--- a/setup.py
+++ b/setup.py
@@ -137,13 +137,13 @@ setup(name=name,
     license='GPL-3',
     python_requires='>=3.7',
     install_requires=requires,
+    extras_require={
+        'test': tests_require,
+        },
     dependency_links=dependency_links,
     zip_safe=False,
     entry_points="""
     [trytond.modules]
     party_relationship = trytond.modules.party_relationship
     """,
-    test_suite='tests',
-    test_loader='trytond.test_loader:Loader',
-    tests_require=tests_require,
     )
diff --git a/tests/__init__.py b/tests/__init__.py
index 9cb64b4448..4effdfa4a2 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -1,10 +1,2 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
-
-try:
-    from trytond.modules.party_relationship.tests.test_party_relationship import \
-        suite  # noqa: E501
-except ImportError:
-    from .test_party_relationship import suite
-
-__all__ = ['suite']
diff --git a/tests/test_party_relationship.py b/tests/test_module.py
similarity index 97%
rename from tests/test_party_relationship.py
rename to tests/test_module.py
index d5e9009a1e..ae327cd8ed 100644
--- a/tests/test_party_relationship.py
+++ b/tests/test_module.py
@@ -5,9 +5,7 @@ import unittest
 
 from trytond import backend
 from trytond.pool import Pool
-from trytond.tests.test_tryton import ModuleTestCase
-from trytond.tests.test_tryton import suite as tryton_suite
-from trytond.tests.test_tryton import with_transaction
+from trytond.tests.test_tryton import ModuleTestCase, with_transaction
 from trytond.transaction import Transaction
 
 
@@ -294,7 +292,4 @@ class TestCase(ModuleTestCase):
                 ['A', 'C', 'B'])
 
 
-def suite():
-    suite = tryton_suite()
-    suite.addTests(unittest.TestLoader().loadTestsFromTestCase(TestCase))
-    return suite
+del ModuleTestCase
diff --git a/tox.ini b/tox.ini
index 48abd4ff09..d5e3bd93b4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -2,8 +2,9 @@
 envlist = {py37,py38,py39,py310}-{sqlite,postgresql}
 
 [testenv]
+extras = test
 commands =
-    coverage run --include=.*/party_relationship/* setup.py test
+    coverage run --include=.*/party_relationship/* -m unittest discover -s tests
     coverage report --include=.*/party_relationship/* --omit=*/tests/*
 deps =
     coverage