Handle TestCase with when using --pdb option (#406)

This commit works around the root cause in Django:
https://code.djangoproject.com/ticket/27391

Author: asfaltboy

pytest_django/plugin.py

@@ -387,6 +387,22 @@ def _django_setup_unittest(request, django_db_blocker):
 
         cls = request.node.cls
 
+        # implement missing (as of 1.10) debug() method for django's TestCase
+        # see pytest-dev/pytest-django#406
+        def _cleaning_debug(self):
+            testMethod = getattr(self, self._testMethodName)
+            skipped = (
+                getattr(self.__class__, "__unittest_skip__", False) or
+                getattr(testMethod, "__unittest_skip__", False))
+
+            if not skipped:
+                self._pre_setup()
+            super(cls, self).debug()
+            if not skipped:
+                self._post_teardown()
+
+        cls.debug = _cleaning_debug
+
         _restore_class_methods(cls)
         cls.setUpClass()
         _disable_class_methods(cls)

tests/test_unittest.py

@@ -235,3 +235,46 @@ class TestCaseWithTrDbFixture(TestCase):
     def test_simple(self):
         # We only want to check setup/teardown does not conflict
         assert 1
+
+
+def test_pdb_enabled(django_testdir):
+    """
+    Make sure the database is flushed and tests are isolated when
+    using the --pdb option.
+
+    See issue #405 for details:
+    https://github.com/pytest-dev/pytest-django/issues/405
+    """
+
+    django_testdir.create_test_module('''
+        import os
+
+        from django.test import TestCase
+        from django.conf import settings
+
+        from .app.models import Item
+
+        class TestPDBIsolation(TestCase):
+            def setUp(self):
+                """setUp should be called after starting a transaction"""
+                assert Item.objects.count() == 0
+                Item.objects.create(name='Some item')
+                Item.objects.create(name='Some item again')
+
+            def test_count(self):
+                self.assertEqual(Item.objects.count(), 2)
+                assert Item.objects.count() == 2
+                Item.objects.create(name='Foo')
+                self.assertEqual(Item.objects.count(), 3)
+
+            def test_count_again(self):
+                self.test_count()
+
+            def tearDown(self):
+                """tearDown should be called before rolling back the database"""
+                assert Item.objects.count() == 3
+
+    ''')
+
+    result = django_testdir.runpytest_subprocess('-v', '--pdb')
+    assert result.ret == 0