modeltest refactoring

01_before.py

class ModelTest(TestCase):

    def test_lookup(self):
        # No articles are in the system yet.
        self.assertQuerysetEqual(Article.objects.all(), [])

        # Create an Article.
        a = Article(
            id=None,
            headline='Area man programs in Python',
            pub_date=datetime(2005, 7, 28),
        )

        # Save it into the database. You have to call save() explicitly.
        a.save()

        # Now it has an ID.
        self.assertTrue(a.id != None)

        # Models have a pk property that is an alias for the primary key
        # attribute (by default, the 'id' attribute).
        self.assertEqual(a.pk, a.id)

        # Access database columns via Python attributes.
        self.assertEqual(a.headline, 'Area man programs in Python')
        self.assertEqual(a.pub_date, datetime(2005, 7, 28, 0, 0))

        # Change values by changing the attributes, then calling save().
        a.headline = 'Area woman programs in Python'
        a.save()

        # Article.objects.all() returns all the articles in the database.
        self.assertQuerysetEqual(Article.objects.all(),
            ['<Article: Area woman programs in Python>'])

        # Django provides a rich database lookup API.
        self.assertEqual(Article.objects.get(id__exact=a.id), a)
        self.assertEqual(Article.objects.get(headline__startswith='Area woman'), a)
        self.assertEqual(Article.objects.get(pub_date__year=2005), a)
        self.assertEqual(Article.objects.get(pub_date__year=2005, pub_date__month=7), a)
        self.assertEqual(Article.objects.get(pub_date__year=2005, pub_date__month=7, pub_date__day=28), a)
        self.assertEqual(Article.objects.get(pub_date__week_day=5), a)

        # The "__exact" lookup type can be omitted, as a shortcut.
        self.assertEqual(Article.objects.get(id=a.id), a)
        self.assertEqual(Article.objects.get(headline='Area woman programs in Python'), a)

        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__year=2005),
            ['<Article: Area woman programs in Python>'],
        )
        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__year=2004),
            [],
        )
        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__year=2005, pub_date__month=7),
            ['<Article: Area woman programs in Python>'],
        )

        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__week_day=5),
            ['<Article: Area woman programs in Python>'],
        )
        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__week_day=6),
            [],
        )

        # Django raises an Article.DoesNotExist exception for get() if the
        # parameters don't match any object.
        self.assertRaisesRegexp(
            ObjectDoesNotExist,
            "Article matching query does not exist. Lookup parameters were "
            "{'id__exact': 2000}",
            Article.objects.get,
            id__exact=2000,
        )
        # To avoid dict-ordering related errors check only one lookup
        # in single assert.
        self.assertRaisesRegexp(
            ObjectDoesNotExist,
            ".*'pub_date__year': 2005.*",
            Article.objects.get,
            pub_date__year=2005,
            pub_date__month=8,
        )
        self.assertRaisesRegexp(
            ObjectDoesNotExist,
            ".*'pub_date__month': 8.*",
            Article.objects.get,
            pub_date__year=2005,
            pub_date__month=8,
        )

        self.assertRaisesRegexp(
            ObjectDoesNotExist,
            "Article matching query does not exist. Lookup parameters were "
            "{'pub_date__week_day': 6}",
            Article.objects.get,
            pub_date__week_day=6,
        )

        # Lookup by a primary key is the most common case, so Django
        # provides a shortcut for primary-key exact lookups.
        # The following is identical to articles.get(id=a.id).
        self.assertEqual(Article.objects.get(pk=a.id), a)

        # pk can be used as a shortcut for the primary key name in any query.
        self.assertQuerysetEqual(Article.objects.filter(pk__in=[a.id]),
            ["<Article: Area woman programs in Python>"])

        # Model instances of the same type and same ID are considered equal.
        a = Article.objects.get(pk=a.id)
        b = Article.objects.get(pk=a.id)
        self.assertEqual(a, b)

02_after.py

class SingleModelTest(TestCase):
    def setUp(self):
        # Create an Article for use in the tests:
        a = Article(
            id=None,
            headline='Area man programs in Python',
            pub_date=datetime(2005, 7, 28),
        )

        # Save it into the database. You have to call save() explicitly.
        a.save()

        self.test_model = a

    def test_model_instance_updated_correctly_after_save(self):
        """
        Ensure that after saving, the model instance has been updated.
        """
        a = self.test_model

        # Now it has an ID.
        self.assertTrue(a.id != None)

        # Models have a pk property that is an alias for the primary key
        # attribute (by default, the 'id' attribute).
        self.assertEqual(a.pk, a.id)

        # Access database columns via Python attributes.
        self.assertEqual(a.headline, 'Area man programs in Python')
        self.assertEqual(a.pub_date, datetime(2005, 7, 28, 0, 0))

    def test_model_updated_in_database(self):
        """
        Ensure that after updating an attribute and saving, newly loaded instances have th updated value.
        """
        a = self.test_model

        # Change values by changing the attributes, then calling save().
        a.headline = 'Area woman programs in Python'
        a.save()

        # Article.objects.all() returns all the articles in the database.
        self.assertQuerysetEqual(Article.objects.all(),
            ['<Article: Area woman programs in Python>'])

    def test_model_objects_get(self):
        """
        Ensure that the saved instance can be loaded from the database using get on its attribute values.
        """
        a = self.test_model

        self.assertEqual(Article.objects.get(id__exact=a.id), a)
        self.assertEqual(Article.objects.get(headline__startswith='Area man'), a)
        self.assertEqual(Article.objects.get(pub_date__year=2005), a)
        self.assertEqual(Article.objects.get(pub_date__year=2005, pub_date__month=7), a)
        self.assertEqual(Article.objects.get(pub_date__year=2005, pub_date__month=7, pub_date__day=28), a)
        self.assertEqual(Article.objects.get(pub_date__week_day=5), a)
        # The "__exact" lookup type can be omitted, as a shortcut.
        self.assertEqual(Article.objects.get(id=a.id), a)
        self.assertEqual(Article.objects.get(headline='Area man programs in Python'), a)

    def test_model_objects_filter(self):
        """
        Ensure that filtering on attribute values return the expected model instances.
        """
        a = self.test_model

        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__year=2005),
            ['<Article: Area man programs in Python>'],
        )
        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__year=2004),
            [],
        )
        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__year=2005, pub_date__month=7),
            ['<Article: Area man programs in Python>'],
        )

        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__week_day=5),
            ['<Article: Area man programs in Python>'],
        )
        self.assertQuerysetEqual(
            Article.objects.filter(pub_date__week_day=6),
            [],
        )
        # pk can be used as a shortcut for the primary key name in any query.
        self.assertQuerysetEqual(Article.objects.filter(pk__in=[a.id]),
            ["<Article: Area man programs in Python>"])

    def test_model_get_exceptions(self):
        """
        Ensure that the correct exceptions and error messages are raised when get cannot load the requested object.
        """

        # Django raises an Article.DoesNotExist exception for get() if the
        # parameters don't match any object.
        self.assertRaisesRegexp(
            ObjectDoesNotExist,
            "Article matching query does not exist. Lookup parameters were "
            "{'id__exact': 2000}",
            Article.objects.get,
            id__exact=2000,
        )
        # To avoid dict-ordering related errors check only one lookup
        # in single assert.
        self.assertRaisesRegexp(
            ObjectDoesNotExist,
            ".*'pub_date__year': 2005.*",
            Article.objects.get,
            pub_date__year=2005,
            pub_date__month=8,
        )
        self.assertRaisesRegexp(
            ObjectDoesNotExist,
            ".*'pub_date__month': 8.*",
            Article.objects.get,
            pub_date__year=2005,
            pub_date__month=8,
        )

        self.assertRaisesRegexp(
            ObjectDoesNotExist,
            "Article matching query does not exist. Lookup parameters were "
            "{'pub_date__week_day': 6}",
            Article.objects.get,
            pub_date__week_day=6,
        )

    def test_model_instances_with_identical_type_and_id_considered_equal(self):
        """
        Ensure model instances of the same type and same ID are considered equal.
        """
        article1 = Article.objects.get(pk=self.test_model.id)
        article2 = Article.objects.get(pk=self.test_model.id)
        self.assertEqual(article1, article2)

    def test_loaded_model_is_equal_to_original_instance(self):
        """
        Ensure that a model loaded from the database is considered equal to the original instance.
        """
        a = self.test_model
        self.assertEqual(Article.objects.get(pk=a.id), a)