text: from __future__ import unicode_literals
  
  from django.test import TestCase
  
  from .models import A, B, D, DataPoint, RelatedPoint, Foo, Bar
  
  
  class SimpleTest(TestCase):
      def setUp(self):
          self.a1 = A.objects.create()
          self.a2 = A.objects.create()
          for x in range(20):
              B.objects.create(a=self.a1)
              D.objects.create(a=self.a1)
  
      def test_nonempty_update(self):
          """
          Test that update changes the right number of rows for a nonempty queryset
          """
          num_updated = self.a1.b_set.update(y=100)
          self.assertEqual(num_updated, 20)
          cnt = B.objects.filter(y=100).count()
          self.assertEqual(cnt, 20)
  
      def test_empty_update(self):
          """
          Test that update changes the right number of rows for an empty queryset
          """
          num_updated = self.a2.b_set.update(y=100)
          self.assertEqual(num_updated, 0)
          cnt = B.objects.filter(y=100).count()
          self.assertEqual(cnt, 0)
  
      def test_nonempty_update_with_inheritance(self):
          """
          Test that update changes the right number of rows for an empty queryset
          when the update affects only a base table
          """
          num_updated = self.a1.d_set.update(y=100)
          self.assertEqual(num_updated, 20)
          cnt = D.objects.filter(y=100).count()
          self.assertEqual(cnt, 20)
  
      def test_empty_update_with_inheritance(self):
          """
          Test that update changes the right number of rows for an empty queryset
          when the update affects only a base table
          """
          num_updated = self.a2.d_set.update(y=100)
          self.assertEqual(num_updated, 0)
          cnt = D.objects.filter(y=100).count()
          self.assertEqual(cnt, 0)
  
      def test_foreign_key_update_with_id(self):
          """
          Test that update works using <field>_id for foreign keys
          """
          num_updated = self.a1.d_set.update(a_id=self.a2)
          self.assertEqual(num_updated, 20)
          self.assertEqual(self.a2.d_set.count(), 20)
  
  
  class AdvancedTests(TestCase):
  
      def setUp(self):
          self.d0 = DataPoint.objects.create(name="d0", value="apple")
          self.d2 = DataPoint.objects.create(name="d2", value="banana")
          self.d3 = DataPoint.objects.create(name="d3", value="banana")
          self.r1 = RelatedPoint.objects.create(name="r1", data=self.d3)
  
      def test_update(self):
          """
          Objects are updated by first filtering the candidates into a queryset
          and then calling the update() method. It executes immediately and
          returns nothing.
          """
          resp = DataPoint.objects.filter(value="apple").update(name="d1")
          self.assertEqual(resp, 1)
          resp = DataPoint.objects.filter(value="apple")
          self.assertEqual(list(resp), [self.d0])
  
      def test_update_multiple_objects(self):
          """
          We can update multiple objects at once.
          """
          resp = DataPoint.objects.filter(value="banana").update(
              value="pineapple")
          self.assertEqual(resp, 2)
          self.assertEqual(DataPoint.objects.get(name="d2").value, 'pineapple')
  
      def test_update_fk(self):
          """
          Foreign key fields can also be updated, although you can only update
          the object referred to, not anything inside the related object.
          """
          resp = RelatedPoint.objects.filter(name="r1").update(data=self.d0)
          self.assertEqual(resp, 1)
          resp = RelatedPoint.objects.filter(data__name="d0")
          self.assertEqual(list(resp), [self.r1])
  
      def test_update_multiple_fields(self):
          """
          Multiple fields can be updated at once
          """
          resp = DataPoint.objects.filter(value="apple").update(
              value="fruit", another_value="peach")
          self.assertEqual(resp, 1)
          d = DataPoint.objects.get(name="d0")
          self.assertEqual(d.value, 'fruit')
          self.assertEqual(d.another_value, 'peach')
  
      def test_update_all(self):
          """
          In the rare case you want to update every instance of a model, update()
          is also a manager method.
          """
          self.assertEqual(DataPoint.objects.update(value='thing'), 3)
          resp = DataPoint.objects.values('value').distinct()
          self.assertEqual(list(resp), [{'value': 'thing'}])
  
      def test_update_slice_fail(self):
          """
          We do not support update on already sliced query sets.
          """
          method = DataPoint.objects.all()[:2].update
          self.assertRaises(AssertionError, method,
                            another_value='another thing')
  
      def test_update_respects_to_field(self):
          """
          Update of an FK field which specifies a to_field works.
          """
          a_foo = Foo.objects.create(target='aaa')
          b_foo = Foo.objects.create(target='bbb')
          bar = Bar.objects.create(foo=a_foo)
          self.assertEqual(bar.foo_id, a_foo.target)
          bar_qs = Bar.objects.filter(pk=bar.pk)
          self.assertEqual(bar_qs[0].foo_id, a_foo.target)
          bar_qs.update(foo=b_foo)
          self.assertEqual(bar_qs[0].foo_id, b_foo.target)
  