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diff --git a/tests/many_to_one_regress/tests.py b/tests/many_to_one_regress/tests.py
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+++ b/tests/many_to_one_regress/tests.py
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+from __future__ import absolute_import
+
+from django.db import models
+from django.test import TestCase
+from django.utils import six
+
+from .models import (
+    First, Third, Parent, Child, Category, Record, Relation, Car, Driver)
+
+
+class ManyToOneRegressionTests(TestCase):
+    def test_object_creation(self):
+        Third.objects.create(id='3', name='An example')
+        parent = Parent(name='fred')
+        parent.save()
+        Child.objects.create(name='bam-bam', parent=parent)
+
+    def test_fk_assignment_and_related_object_cache(self):
+        # Tests of ForeignKey assignment and the related-object cache (see #6886).
+
+        p = Parent.objects.create(name="Parent")
+        c = Child.objects.create(name="Child", parent=p)
+
+        # Look up the object again so that we get a "fresh" object.
+        c = Child.objects.get(name="Child")
+        p = c.parent
+
+        # Accessing the related object again returns the exactly same object.
+        self.assertTrue(c.parent is p)
+
+        # But if we kill the cache, we get a new object.
+        del c._parent_cache
+        self.assertFalse(c.parent is p)
+
+        # Assigning a new object results in that object getting cached immediately.
+        p2 = Parent.objects.create(name="Parent 2")
+        c.parent = p2
+        self.assertTrue(c.parent is p2)
+
+        # Assigning None succeeds if field is null=True.
+        p.bestchild = None
+        self.assertTrue(p.bestchild is None)
+
+        # bestchild should still be None after saving.
+        p.save()
+        self.assertTrue(p.bestchild is None)
+
+        # bestchild should still be None after fetching the object again.
+        p = Parent.objects.get(name="Parent")
+        self.assertTrue(p.bestchild is None)
+
+        # Assigning None fails: Child.parent is null=False.
+        self.assertRaises(ValueError, setattr, c, "parent", None)
+
+        # You also can't assign an object of the wrong type here
+        self.assertRaises(ValueError, setattr, c, "parent", First(id=1, second=1))
+
+        # Nor can you explicitly assign None to Child.parent during object
+        # creation (regression for #9649).
+        self.assertRaises(ValueError, Child, name='xyzzy', parent=None)
+        self.assertRaises(ValueError, Child.objects.create, name='xyzzy', parent=None)
+
+        # Trying to assign to unbound attribute raises AttributeError
+        six.assertRaisesRegex(self, AttributeError, "must be accessed via instance",
+            Child.parent.__set__, None, p)
+
+        # Creation using keyword argument should cache the related object.
+        p = Parent.objects.get(name="Parent")
+        c = Child(parent=p)
+        self.assertTrue(c.parent is p)
+
+        # Creation using keyword argument and unsaved related instance (#8070).
+        p = Parent()
+        c = Child(parent=p)
+        self.assertTrue(c.parent is p)
+
+        # Creation using attname keyword argument and an id will cause the
+        # related object to be fetched.
+        p = Parent.objects.get(name="Parent")
+        c = Child(parent_id=p.id)
+        self.assertFalse(c.parent is p)
+        self.assertEqual(c.parent, p)
+
+    def test_multiple_foreignkeys(self):
+        # Test of multiple ForeignKeys to the same model (bug #7125).
+        c1 = Category.objects.create(name='First')
+        c2 = Category.objects.create(name='Second')
+        c3 = Category.objects.create(name='Third')
+        r1 = Record.objects.create(category=c1)
+        r2 = Record.objects.create(category=c1)
+        r3 = Record.objects.create(category=c2)
+        r4 = Record.objects.create(category=c2)
+        r5 = Record.objects.create(category=c3)
+        r = Relation.objects.create(left=r1, right=r2)
+        r = Relation.objects.create(left=r3, right=r4)
+        r = Relation.objects.create(left=r1, right=r3)
+        r = Relation.objects.create(left=r5, right=r2)
+        r = Relation.objects.create(left=r3, right=r2)
+
+        q1 = Relation.objects.filter(left__category__name__in=['First'], right__category__name__in=['Second'])
+        self.assertQuerysetEqual(q1, ["<Relation: First - Second>"])
+
+        q2 = Category.objects.filter(record__left_set__right__category__name='Second').order_by('name')
+        self.assertQuerysetEqual(q2, ["<Category: First>", "<Category: Second>"])
+
+        p = Parent.objects.create(name="Parent")
+        c = Child.objects.create(name="Child", parent=p)
+        self.assertRaises(ValueError, Child.objects.create, name="Grandchild", parent=c)
+
+    def test_fk_instantiation_outside_model(self):
+        # Regression for #12190 -- Should be able to instantiate a FK outside
+        # of a model, and interrogate its related field.
+        cat = models.ForeignKey(Category)
+        self.assertEqual('id', cat.rel.get_related_field().name)
+
+    def test_relation_unsaved(self):
+        # Test that the <field>_set manager does not join on Null value fields (#17541)
+        Third.objects.create(name='Third 1')
+        Third.objects.create(name='Third 2')
+        th = Third(name="testing")
+        # The object isn't saved an thus the relation field is null - we won't even
+        # execute a query in this case.
+        with self.assertNumQueries(0):
+            self.assertEqual(th.child_set.count(), 0)
+        th.save()
+        # Now the model is saved, so we will need to execute an query.
+        with self.assertNumQueries(1):
+            self.assertEqual(th.child_set.count(), 0)
+
+    def test_related_null_to_field(self):
+        c1 = Car.objects.create()
+        c2 = Car.objects.create()
+        d1 = Driver.objects.create()
+        self.assertIs(d1.car, None)
+        with self.assertNumQueries(0):
+            self.assertEqual(list(c1.drivers.all()), [])