Migrated null_fk doctests. Thanks to Stephan Jaekel.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13934 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/null_fk/tests.py

@@ -0,0 +1,42 @@
+from django.test import TestCase
+
+from regressiontests.null_fk.models import *
+
+class NullFkTests(TestCase):
+
+    def test_null_fk(self):
+        d = SystemDetails.objects.create(details='First details')
+        s = SystemInfo.objects.create(system_name='First forum', system_details=d)
+        f = Forum.objects.create(system_info=s, forum_name='First forum')
+        p = Post.objects.create(forum=f, title='First Post')
+        c1 = Comment.objects.create(post=p, comment_text='My first comment')
+        c2 = Comment.objects.create(comment_text='My second comment')
+
+        # Starting from comment, make sure that a .select_related(...) with a specified
+        # set of fields will properly LEFT JOIN multiple levels of NULLs (and the things
+        # that come after the NULLs, or else data that should exist won't). Regression
+        # test for #7369.
+        c = Comment.objects.select_related().get(id=1)
+        self.assertEquals(c.post, p)
+        self.assertEquals(Comment.objects.select_related().get(id=2).post, None)
+
+        self.assertQuerysetEqual(
+            Comment.objects.select_related('post__forum__system_info').all(),
+            [
+                (1, u'My first comment', '<Post: First Post>'),
+                (2, u'My second comment', 'None')
+            ],
+            transform = lambda c: (c.id, c.comment_text, repr(c.post))
+        )
+
+        # Regression test for #7530, #7716.
+        self.assertTrue(Comment.objects.select_related('post').filter(post__isnull=True)[0].post is None)
+
+        self.assertQuerysetEqual(
+            Comment.objects.select_related('post__forum__system_info__system_details'),
+            [
+                (1, u'My first comment', '<Post: First Post>'),
+                (2, u'My second comment', 'None')
+            ],
+            transform = lambda c: (c.id, c.comment_text, repr(c.post))
+        )