TetNullPagination

class TestForwardNullPagination(TestCase):
    @classmethod
    def setUpTestData(cls):
        now = timezone.now()
        cls.items = []
        for i in range(2):  # index 0-1
            author = Author.objects.create(name='Name %s' % i, age=i+20, created=now - datetime.timedelta(hours=i))
            cls.items.append(author)
        for i in range(5):  # index 2-6
            author = Author.objects.create(name='NameNull %s' % (i + 2), age=None, created=now - datetime.timedelta(hours=i))
            cls.items.append(author)
        cls.paginator = CursorPaginator(Author.objects.all(), ('-age', '-created',))
    # [1, 0, 2, 3, 4, 5, 6]
    

    def test_first_page(self):
        page = self.paginator.page(first=3)
        self.assertSequenceEqual(page, [self.items[1], self.items[0], self.items[2]])
        self.assertTrue(page.has_next)
        self.assertFalse(page.has_previous)

    def test_second_page(self):
        previous_page = self.paginator.page(first=3)
        cursor = self.paginator.cursor(previous_page[-1])
        page = self.paginator.page(first=2, after=cursor)
        self.assertSequenceEqual(page, [self.items[3], self.items[4]])
        self.assertTrue(page.has_next)
        self.assertTrue(page.has_previous)

    def test_last_page(self):
        previous_page = self.paginator.page(first=5)
        cursor = self.paginator.cursor(previous_page[-1])
        page = self.paginator.page(first=10, after=cursor)
        self.assertSequenceEqual(page, [self.items[5], self.items[6]])
        self.assertFalse(page.has_next)
        self.assertTrue(page.has_previous)


class TestBackwardsNullPagination(TestCase):
    @classmethod
    def setUpTestData(cls):
        now = timezone.now()
        cls.items = []
        for i in range(2):  # index 0-1
            author = Author.objects.create(name='Name %s' % i, age=i+20, created=now - datetime.timedelta(hours=i))
            cls.items.append(author)
        for i in range(5):  # index 2-6
            author = Author.objects.create(name='NameNull %s' % (i + 2), age=None, created=now - datetime.timedelta(hours=i))
            cls.items.append(author)
        cls.paginator = CursorPaginator(Author.objects.all(), ('-age', '-created',))

    # [1, 0, 2, 3, 4, 5, 6]

    def test_first_page(self):
        page = self.paginator.page(last=2)
        self.assertSequenceEqual(page, [self.items[5], self.items[6]])
        self.assertTrue(page.has_previous)
        self.assertFalse(page.has_next)

    def test_second_page(self):
        previous_page = self.paginator.page(last=2)
        cursor = self.paginator.cursor(previous_page[0])
        page = self.paginator.page(last=4, before=cursor)
        self.assertSequenceEqual(page, [self.items[0], self.items[2], self.items[3], self.items[4]])
        self.assertTrue(page.has_previous)
        self.assertTrue(page.has_next)

    def test_last_page(self):
        previous_page = self.paginator.page(last=6)
        cursor = self.paginator.cursor(previous_page[0])
        page = self.paginator.page(last=10, before=cursor)
        self.assertSequenceEqual(page, [self.items[1]])
        self.assertFalse(page.has_previous)
        self.assertTrue(page.has_next)