diff --git a/tests/test_ctl.py b/tests/test_ctl.py
index c8c36d75c..c841b0883 100644
--- a/tests/test_ctl.py
+++ b/tests/test_ctl.py
@@ -438,13 +438,13 @@ def test_shell():
         call_command('shell')  # missing tenant name
 
 
-class TestAfterJob(AfterJob):
+class AfterJobForTest(AfterJob):
     def execute(self):
         self.test_result = WorkflowStatusItem().compute('{{ global_title|default:"FAIL" }}')
         self.l10n_month = WorkflowStatusItem().compute('{{ "10/10/2010"|date:"F" }}')
 
 
-class TestExceptionAfterJob(AfterJob):
+class AfterJobForTestWithException(AfterJob):
     def execute(self):
         raise ZeroDivisionError()
 
@@ -462,7 +462,7 @@ def test_runjob(pub):
     with open(os.path.join(pub.app_dir, 'site-options.cfg'), 'w') as fd:
         pub.site_options.write(fd)
 
-    job = TestAfterJob(label='test')
+    job = AfterJobForTest(label='test')
     job.store()
     assert AfterJob.get(job.id).status == 'registered'
     call_command('runjob', '--domain=example.net', '--job-id=%s' % job.id)
@@ -472,7 +472,7 @@ def test_runjob(pub):
 
     pub.cfg['language'] = {'language': 'fr'}
     pub.write_cfg()
-    job = TestAfterJob(label='test2')
+    job = AfterJobForTest(label='test2')
     job.store()
     assert AfterJob.get(job.id).status == 'registered'
     call_command('runjob', '--domain=example.net', '--job-id=%s' % job.id)
@@ -489,7 +489,7 @@ def test_runjob(pub):
     assert AfterJob.get(job.id).completion_time != completion_time
 
     # test exception handling
-    job = TestExceptionAfterJob(label='test3')
+    job = AfterJobForTestWithException(label='test3')
     job.store()
     assert AfterJob.get(job.id).status == 'registered'
     call_command('runjob', '--domain=example.net', '--job-id=%s' % job.id)
diff --git a/tox.ini b/tox.ini
index 8e149de15..211772010 100644
--- a/tox.ini
+++ b/tox.ini
@@ -73,3 +73,7 @@ deps =
 commands =
     ./getlasso3.sh
     ./pylint.sh wcs/ tests/
+
+[pytest]
+filterwarnings =
+  error::_pytest.warning_types.PytestCollectionWarning
diff --git a/wcs/testdef.py b/wcs/testdef.py
index e704d787c..45f849311 100644
--- a/wcs/testdef.py
+++ b/wcs/testdef.py
@@ -36,6 +36,9 @@ class TestError(Exception):
         self.msg = msg
         self.error = error
 
+    # prevent pytest from trying to collect this class (#75521)
+    __test__ = False
+
 
 class TestDef(sql.TestDef):
     _names = 'testdef'