From fcd08c175787e909b3eb98f756317a07741c48dd Mon Sep 17 00:00:00 2001
From: Jon Dufresne <jon.dufresne@gmail.com>
Date: Fri, 12 Feb 2016 16:41:31 -0800
Subject: [PATCH] Fixed #11665 -- Made TestCase check deferrable constraints
 after each test.

---
 django/test/testcases.py          | 13 ++++++++++++-
 docs/releases/1.10.txt            |  6 +++++-
 docs/topics/testing/tools.txt     |  7 +++++++
 tests/auth_tests/test_views.py    |  6 ++++++
 tests/test_utils/test_testcase.py | 20 ++++++++++++++++++++
 5 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 tests/test_utils/test_testcase.py

diff --git a/django/test/testcases.py b/django/test/testcases.py
index 34c94b82cc4..9de29fff683 100644
--- a/django/test/testcases.py
+++ b/django/test/testcases.py
@@ -1044,7 +1044,18 @@ class TestCase(TransactionTestCase):
     def _fixture_teardown(self):
         if not connections_support_transactions():
             return super(TestCase, self)._fixture_teardown()
-        self._rollback_atomics(self.atomics)
+        try:
+            for db_name in reversed(self._databases_names()):
+                if self._should_check_constraints(connections[db_name]):
+                    connections[db_name].check_constraints()
+        finally:
+            self._rollback_atomics(self.atomics)
+
+    def _should_check_constraints(self, connection):
+        return (
+            connection.features.can_defer_constraint_checks and
+            not connection.needs_rollback and connection.is_usable()
+        )
 
 
 class CheckCondition(object):
diff --git a/docs/releases/1.10.txt b/docs/releases/1.10.txt
index db4f7d4632d..b3bd4b8afd8 100644
--- a/docs/releases/1.10.txt
+++ b/docs/releases/1.10.txt
@@ -333,7 +333,8 @@ Templates
 Tests
 ~~~~~
 
-* ...
+* To better catch bugs, :class:`~django.test.TestCase` now checks deferrable
+  database constraints at the end of each test.
 
 URLs
 ~~~~
@@ -541,6 +542,9 @@ Miscellaneous
   aggregate function now returns a ``float`` instead of ``decimal.Decimal``.
   (It's still wrapped in a measure of square meters.)
 
+* Tests that violate deferrable database constraints will now error when run on
+  a database that supports deferrable constraints.
+
 .. _deprecated-features-1.10:
 
 Features deprecated in 1.10
diff --git a/docs/topics/testing/tools.txt b/docs/topics/testing/tools.txt
index 5b8908c4855..2bb53454cf3 100644
--- a/docs/topics/testing/tools.txt
+++ b/docs/topics/testing/tools.txt
@@ -761,11 +761,18 @@ additions, including:
 * Wraps the tests within two nested ``atomic`` blocks: one for the whole class
   and one for each test.
 
+* Checks deferrable database constraints at the end of each test.
+
 * Creates a TestClient instance.
 
 * Django-specific assertions for testing for things like redirection and form
   errors.
 
+.. versionchanged:: 1.10
+
+    The check for deferrable database constraints at the end of each test was
+    added.
+
 .. classmethod:: TestCase.setUpTestData()
 
     The class-level ``atomic`` block described above allows the creation of
diff --git a/tests/auth_tests/test_views.py b/tests/auth_tests/test_views.py
index 7fd493ca34a..d8325d8b93f 100644
--- a/tests/auth_tests/test_views.py
+++ b/tests/auth_tests/test_views.py
@@ -991,3 +991,9 @@ class UUIDUserTests(TestCase):
         self.assertEqual(row.user_id, 1)  # hardcoded in CustomUserAdmin.log_change()
         self.assertEqual(row.object_id, str(u.pk))
         self.assertEqual(row.get_change_message(), 'Changed password.')
+
+        # The LogEntry.user column isn't altered to a UUID type so it's set to
+        # an integer manually in CustomUserAdmin to avoid an error. To avoid a
+        # constraint error, delete the entry before constraints are checked
+        # after the test.
+        row.delete()
diff --git a/tests/test_utils/test_testcase.py b/tests/test_utils/test_testcase.py
new file mode 100644
index 00000000000..8a367391cbf
--- /dev/null
+++ b/tests/test_utils/test_testcase.py
@@ -0,0 +1,20 @@
+from django.db import IntegrityError, transaction
+from django.test import TestCase, skipUnlessDBFeature
+
+from .models import PossessedCar
+
+
+class TestTestCase(TestCase):
+
+    @skipUnlessDBFeature('can_defer_constraint_checks')
+    @skipUnlessDBFeature('supports_foreign_keys')
+    def test_fixture_teardown_checks_constraints(self):
+        rollback_atomics = self._rollback_atomics
+        self._rollback_atomics = lambda connection: None  # noop
+        try:
+            car = PossessedCar.objects.create(car_id=1, belongs_to_id=1)
+            with self.assertRaises(IntegrityError), transaction.atomic():
+                self._fixture_teardown()
+            car.delete()
+        finally:
+            self._rollback_atomics = rollback_atomics