Fix autouse fixtures running in @unittest.skip classes

changelog/13885.bugfix.rst

@@ -0,0 +1 @@
+Fixed autouse fixtures defined inside a :class:`unittest.TestCase` class running even when the class is decorated with :func:`unittest.skip` or :func:`unittest.skipIf` -- regression since pytest 8.1.0.

src/_pytest/unittest.py

@@ -100,6 +100,8 @@ def collect(self) -> Iterable[Item | Collector]:
             self._register_unittest_setup_method_fixture(cls)
             self._register_unittest_setup_class_fixture(cls)
             self._register_setup_class_fixture()
+        else:
+            self._register_unittest_skip_fixture(cls)
 
         self.session._fixturemanager.parsefactories(self.newinstance(), self.nodeid)
 
@@ -175,6 +177,22 @@ def unittest_setup_class_fixture(
             autouse=True,
         )
 
+    def _register_unittest_skip_fixture(self, cls: type) -> None:
+        """Register an auto-use fixture to skip tests for a class decorated
+        with @unittest.skip or @unittest.skipIf (#13885)."""
+
+        def unittest_skip_fixture(request: FixtureRequest) -> None:
+            reason = cls.__unittest_skip_why__
+            raise skip.Exception(reason, _use_item_location=True)
+
+        self.session._fixturemanager._register_fixture(
+            name=f"_unittest_skip_fixture_{cls.__qualname__}",
+            func=unittest_skip_fixture,
+            nodeid=self.nodeid,
+            scope="class",
+            autouse=True,
+        )
+
     def _register_unittest_setup_method_fixture(self, cls: type) -> None:
         """Register an auto-use fixture to invoke setup_method and
         teardown_method (#517)."""

testing/test_unittest.py

@@ -244,6 +244,27 @@ def tearDownClass(self):
     reprec.assertoutcome(skipped=1)
 
 
+def test_unittest_skip_with_autouse_fixture(pytester: Pytester) -> None:
+    """Autouse fixtures inside a @unittest.skipIf class should not run (#13885)."""
+    pytester.makepyfile(
+        """
+        import unittest
+        import pytest
+
+        @unittest.skipIf(True, "skip reason")
+        class TestSkipped(unittest.TestCase):
+            @pytest.fixture(autouse=True)
+            def my_fixture(self):
+                raise RuntimeError("fixture should not run")
+
+            def test_one(self):
+                pass
+    """
+    )
+    reprec = pytester.inline_run()
+    reprec.assertoutcome(skipped=1)
+
+
 def test_method_and_teardown_failing_reporting(pytester: Pytester) -> None:
     pytester.makepyfile(
         """