Fixed #19462 -- Made assertQuerysetEqual detect undefined ordering

If there are more than one values to compare against and the qs isn't
ordered then assertQuerysetEqual will raise a ValueError.

tests/regressiontests/test_utils/tests.py

@@ -54,6 +54,46 @@ class AssertNumQueriesTests(TestCase):
         self.assertNumQueries(2, test_func)
 
 
+class AssertQuerysetEqualTests(TestCase):
+    def setUp(self):
+        self.p1 = Person.objects.create(name='p1')
+        self.p2 = Person.objects.create(name='p2')
+
+    def test_ordered(self):
+        self.assertQuerysetEqual(
+            Person.objects.all().order_by('name'),
+            [repr(self.p1), repr(self.p2)]
+        )
+
+    def test_unordered(self):
+        self.assertQuerysetEqual(
+            Person.objects.all().order_by('name'),
+            [repr(self.p2), repr(self.p1)],
+            ordered=False
+        )
+
+    def test_transform(self):
+        self.assertQuerysetEqual(
+            Person.objects.all().order_by('name'),
+            [self.p1.pk, self.p2.pk],
+            transform=lambda x: x.pk
+        )
+
+    def test_undefined_order(self):
+        # Using an unordered queryset with more than one ordered value
+        # is an error.
+        with self.assertRaises(ValueError):
+            self.assertQuerysetEqual(
+                Person.objects.all(),
+                [repr(self.p1), repr(self.p2)]
+            )
+        # No error for one value.
+        self.assertQuerysetEqual(
+            Person.objects.filter(name='p1'),
+            [repr(self.p1)]
+        )
+
+
 class AssertNumQueriesContextManagerTests(TestCase):
     urls = 'regressiontests.test_utils.urls'