Monkeypatch pytest instead of Django to workaround pytest bug (#782)

Fixes pytest-dev/pytest-django#772.
Ref: pytest-dev/pytest#5996

pytest_django/plugin.py

@@ -518,29 +518,24 @@ def _django_setup_unittest(request, django_db_blocker):
         yield
         return
 
-    request.getfixturevalue("django_db_setup")
+    from _pytest.unittest import TestCaseFunction
 
-    cls = request.node.cls
+    if "debug" in TestCaseFunction.runtest.__code__.co_names:
+        # Fix pytest (https://github.com/pytest-dev/pytest/issues/5991), only
+        # if "self._testcase.debug()" is being used (forward compatible).
+        from _pytest.monkeypatch import MonkeyPatch
 
-    # Implement missing debug() wrapper/method for Django's TestCase (< 3.1.0).
-    # See pytest-dev/pytest-django#406.
-    import django
-    monkeypatch_debug = django.VERSION < (3, 1)
-    if monkeypatch_debug:
-        def _cleaning_debug(self):
-            testMethod = getattr(self, self._testMethodName)
-            skipped = getattr(self.__class__, "__unittest_skip__", False) or getattr(
-                testMethod, "__unittest_skip__", False
-            )
+        def non_debugging_runtest(self):
+            self._testcase(result=self)
 
-            if not skipped:
-                self._pre_setup()
-            super(cls, self).debug()
-            if not skipped:
-                self._post_teardown()
+        mp_debug = MonkeyPatch()
+        mp_debug.setattr("_pytest.unittest.TestCaseFunction.runtest", non_debugging_runtest)
+    else:
+        mp_debug = None
 
-        orig_debug = cls.debug
-        cls.debug = _cleaning_debug
+    request.getfixturevalue("django_db_setup")
+
+    cls = request.node.cls
 
     with django_db_blocker.unblock():
         if _handle_unittest_methods:
@@ -555,8 +550,8 @@ def _cleaning_debug(self):
         else:
             yield
 
-    if monkeypatch_debug:
-        cls.debug = orig_debug
+    if mp_debug:
+        mp_debug.undo()
 
 
 @pytest.fixture(scope="function", autouse=True)

tests/test_unittest.py

@@ -458,7 +458,7 @@ def tearDown(self):
     assert result.ret == 0
 
 
-def test_debug_restored(django_testdir):
+def test_debug_not_used(django_testdir):
     django_testdir.create_test_module(
         """
         from django.test import TestCase
@@ -468,22 +468,14 @@ def test_debug_restored(django_testdir):
 
         class TestClass1(TestCase):
 
-            def test_method(self):
-                pass
-
-
-        class TestClass2(TestClass1):
-
-            def _pre_setup(self):
-                global pre_setup_count
-                pre_setup_count += 1
-                super(TestClass2, self)._pre_setup()
+            def debug(self):
+                assert 0, "should not be called"
 
             def test_method(self):
-                assert pre_setup_count == 1
+                pass
     """
     )
 
     result = django_testdir.runpytest_subprocess("--pdb")
-    result.stdout.fnmatch_lines(["*= 2 passed in *"])
+    result.stdout.fnmatch_lines(["*= 1 passed in *"])
     assert result.ret == 0