Fix setUpClass being called in subclasses that were skipped

Fix #4700

changelog/4700.bugfix.rst

@@ -0,0 +1,2 @@
+Fix regression where ``setUpClass`` would always be called in subclasses even if all tests
+were skipped by a ``unittest.skip()`` decorator applied in the subclass.

src/_pytest/unittest.py

@@ -87,6 +87,9 @@ def _make_xunit_fixture(obj, setup_name, teardown_name, scope, pass_self):
 
     @pytest.fixture(scope=scope, autouse=True)
     def fixture(self, request):
+        if getattr(self, "__unittest_skip__", None):
+            reason = self.__unittest_skip_why__
+            pytest.skip(reason)
         if setup is not None:
             if pass_self:
                 setup(self, request.function)

testing/example_scripts/unittest/test_setup_skip.py

@@ -0,0 +1,13 @@
+"""Skipping an entire subclass with unittest.skip() should *not* call setUp from a base class."""
+import unittest
+
+
+class Base(unittest.TestCase):
+    def setUp(self):
+        assert 0
+
+
+@unittest.skip("skip all tests")
+class Test(Base):
+    def test_foo(self):
+        assert 0

testing/example_scripts/unittest/test_setup_skip_class.py

@@ -0,0 +1,14 @@
+"""Skipping an entire subclass with unittest.skip() should *not* call setUpClass from a base class."""
+import unittest
+
+
+class Base(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        assert 0
+
+
+@unittest.skip("skip all tests")
+class Test(Base):
+    def test_foo(self):
+        assert 0

testing/example_scripts/unittest/test_setup_skip_module.py

@@ -0,0 +1,12 @@
+"""setUpModule is always called, even if all tests in the module are skipped"""
+import unittest
+
+
+def setUpModule():
+    assert 0
+
+
+@unittest.skip("skip all tests")
+class Base(unittest.TestCase):
+    def test(self):
+        assert 0

testing/test_unittest.py

@@ -1026,3 +1026,18 @@ def test_error_message_with_parametrized_fixtures(testdir):
             "*Function type: TestCaseFunction",
         ]
     )
+
+
+@pytest.mark.parametrize(
+    "test_name, expected_outcome",
+    [
+        ("test_setup_skip.py", "1 skipped"),
+        ("test_setup_skip_class.py", "1 skipped"),
+        ("test_setup_skip_module.py", "1 error"),
+    ],
+)
+def test_setup_inheritance_skipping(testdir, test_name, expected_outcome):
+    """Issue #4700"""
+    testdir.copy_example("unittest/{}".format(test_name))
+    result = testdir.runpytest()
+    result.stdout.fnmatch_lines("* {} in *".format(expected_outcome))